Compositions and methods for enhancing transport through mucus

ABSTRACT

The invention generally relates to compositions and methods for transporting substances across mucosal barriers. The invention also relates to methods of making and using such substances.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/843,282, filed Sep. 8, 2006, the specification of which is herebyincorporated herein by reference in its entirety.

BACKGROUND

Organs exposed to the external environment, including the lung airways,nasal respiratory tract, gastrointestinal tract, and cervical vaginaltract are protected from entry of foreign particles (including somepathogens and toxins) by a highly viscous and elastic mucus gel. Humanmucus has evolved to trap foreign particles sterically and/or byadhesion, and then clear them from the body before they reach theunderlying epithelia; particles trapped in mucus can also undergobacterial or enzymatic degradation. Although clearance rates areanatomically determined, mucus turnover rates in the GI tract areestimated as between 24 and 48 h. In the lungs, clearance rates aredependent on the region of particle deposition; however, normal trachealmucus velocities, albeit more rapid than mucus velocities in theperipheral lung, range from 1-10 mm/min and turnover times are less than1 h. As a result, the mucus barrier has been cited as a criticalbottleneck in the treatment of a variety of diseases.

The primary component of mucus is higher molecular weight mucinglycoproteins, which form numerous covalent and noncovalent bonds withother mucin molecules and various constituents, including DNA, alginate,and hyaluronan. (Hanes et al., Gene therapy in the lung, inPharmaceutical Inhalation Aerosol Technology, 2d ed.; Marcel DekkerInc.: New York, 2003; pp. 489-539, incorporated herein by reference).The dense, complex microstructure and high density of hydrophobic andnegatively charged domains give rise to a highly viscoelastic andadhesive gel, which significantly impedes the transport rates of largemacromolecules and nanoparticles. (Saltzman et al., Biophys. J. 1994,66, 508-515; Sanders et al., Am. J. Respir. Crit. Care Med. 2002, 162,1905-1911; Olmsted et al., Biophys. J. 2001 81, 1930-1937 all of whichare incorporated herein by reference). To overcome the mucus barrier,drug carriers must quickly traverse mucus layers that are up to a fewhundred microns thick in order to reach the underlying epithelia andavoid clearance mechanisms. Difficulty in drug-carrier particletransport through mucus is thought to be due to a very small averagemesh pore size (estimates range from 5-10 nm to no larger than 200 nm)of highly elastic human mucus, and to its strongly adhesive nature(Olmsted, S. S., J. L. Padgett, A. I. Yudin, K. J. Whaley, T. R. Moench,and R. A. Cone, Diffusion of macromolecules and virus-like particles inhuman cervical mucus. Biophysical Journal, 2001. 81(4): p. 1930-1937).Cone and coworkers recently showed that standard latex (i.e.,polystyrene) polymer particles as small as 59 nm in diameter arecompletely immobile in mucus since they firmly adhere to mucin fibers,causing it to assemble into mucus strands, or “bundles”. Theseobservations have suggested that efficient transport of syntheticpolymer nanoparticles, especially those larger than 59 nm, through humanmucus barriers is a daunting task.

SUMMARY OF THE INVENTION

The present invention relates in part to the finding thatsurface-altering agents can be used to decrease the mucoadhesion of asubstance and increase its mobility in mucus. Thus, in one aspect theinvention provides a particle modified with one or more surface-alteringmoieties that facilitate passage of the particle through mucus. Suchparticles, e.g., nanoparticles or microparticles, have a higherconcentration of surface moieties than has been previously achieved,leading to the unexpected property of rapid diffusion through mucus. Thepresent invention further comprises a method of producing such particlesand methods of using such particles to treat a patient.

In certain embodiments, the present invention provides surface-alteredparticles and methods of making and using them. Suitable particlesinclude polymeric, liposomal, metal, metal oxide, viral, or quantum dotparticles, or any combination thereof, that are capable of efficientlytraversing mucus layers coating mucosal surfaces. In certainembodiments, such particles may comprise one or more bioactive agents,which may be disposed on the surface of the particle or in the interiorof the particle, e.g., encapsulated in a vehicle, such as a polymer. Incertain embodiments, the one or more bioactive agents are covalently ornon-covalently associated with the particle. Suitable polymericparticles may comprise a pharmaceutically acceptable polymer core and asurface-altering agent. Liposomal particles generally comprise aliposome core and a surface-altering agent. Particles may comprise oneor more bioactive agents and/or imaging agents. The surface-alteringagent may comprise one or more chemical entities, or may, for example,be incorporated (e.g., physically, as a mixture, or covalently, such asa block copolymer or a covalently modified polymer) into the polymervehicle. The particles may also comprise one or more targeting moieties.

Certain embodiments provide particles that are, on average, greater than1, 2, 5, 10, 20, 50, 55, 59, 75, 100, 150, 200, 300, 400, 500, 750,1000, 2000, or 5000 nm in diameter, or that have a diameter intermediatebetween any of these values. In certain embodiments, the particles havean average diameter less than 10,000 nm or 50,000 nm. Certainembodiments provide particles that are, on average, larger than thelargest estimated mucal pore size, which is 100 nm. In certainembodiments, the diameter is the physical diameter. In such embodiments,the diameter of a nonspherical particle is the largest linear distancebetween two points on the surface of the particle. In certainembodiments, the diameter is the hydrodynamic diameter. In certainembodiments, the diameter of a nonspherical particle is the hydrodynamicdiameter.

In certain embodiments, the present invention provides a particle thatcan diffuse through a mucosal barrier at a greater rate or diffusivitythan a corresponding particle, e.g., unmodified polystyrene particles. Aparticle of the invention may pass through a mucosal barrier at a rateor diffusivity that is at least 10, 20, 30, 50, 100, 200, 500, 1000,2000, 5000, 10000—or greater fold higher than a corresponding particle,in addition, a particle of the invention may pass through a mucosalbarrier with a geometric mean squared displacement that is at least 10,20, 30, 50, 100, 200, 500, 1000, 2000, 5000, 10000—or grater fold higherthan a corresponding particle at a time scale of 1 s. The correspondingparticle may comprise a carboxyl-modified polystyrene particle, anamine-modified polystyrene particle, or a sulfate-aldehyde modifiedpolystyrene particle. Such a carboxyl-modified particle preferably hascarboxyl groups present at a density of 1.77 to 6.69 carboxyls per nm².For the purposes of such comparison, The corresponding particle may beapproximately the same size, shape, and/or density as the particle ofthe invention.

In certain embodiments, the present invention provides particles thatcan diffuse through a mucosal barrier at rate approaching the rate ordiffusivity at which said particles can diffuse through water. Aparticle of the invention may pass through a mucosal barrier at a rateor diffusivity that is at least 1/1000, 1/600, 1/500, 1/200, 1/100,1/50, 1/20, 1/10, 1/5, 1/2, or 1 times the rate of the particle in waterunder identical conditions.

In certain embodiments, the present invention provides particlescomprising a surface-altering agent at a given density. A particle ofthe invention may comprise a surface-altering agent at a density of atleast 0.001, 0.002, 0,005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10,20, 50, or 100 units per nm².

In certain embodiments, the present invention provides particles thattravel through mucus, such as human cervicovaginal mucus, at certainabsolute diffusivities. For example, the particles of the presentinvention may travel at diffusivities of at least 1×10⁻⁴, 2×10⁻⁴,5×10⁻⁴, 1×10⁻³, 2×10⁻³, 5×10⁻³, 1×10⁻², 2×10⁻², 4×10⁻², 5×10⁻², 6×10⁻²,8×10⁻², 1×10⁻¹, 2×10⁻¹, 5×10⁻¹, 1, or 2 μm²/s at a time scale of 1 s.

In certain embodiments, the present invention provides particlescomprising a surface-altering agent wherein the mass of thesurface-altering moiety makes up at least 1/10,000, 1/5000, 1/3400,1/2000, 1/1000, 1/500, 1/200, 1/100, 1/50, 1/20, 1/5, 1/2, or 9/10 ofthe mass of the particle.

In certain embodiments, the present invention provides particlescomprising a surface-altering agent that inhibits the adsorption offluorescently labeled avidin, wherein the particle adsorbs less than99%, 95%, 90%, 70%, 50%, 40%, 30%, 20%, 15%, 10%, 8%, 6%, 5%, 4%, 3%,2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the amount of fluorescentlylabeled avidin that is adsorbed by a corresponding particle lacking thesurface-altering agent, as calculated by average maximum fluorescentintensity.

In certain embodiments, the present invention provides particlescomprising a surface-altering agent that affects the zeta-potential ofthe particle, wherein the zeta potential of said particle is between−100 mV and 10 mV, between −50 mV and 10 mV, between −25 mV and 10 mV,between −20 mV and 5 mV, between −10 mV and 10 mV, between −10 mV and 5mV, between −5 mV and 5 mV, or even between −2 mV and 2 mV. Theinvention further comprises said particle wherein the zeta potential ofsaid particle is less than 5 mV. The invention further comprises saidparticle wherein the zeta potential of said particle is less than 10 mV.

In certain embodiments, the present invention provides the particles ofany preceding paragraph, wherein the exponent of a power law fit of themean squared displacement of the particle population as a function oftime scales from 0.067 s to 3.0 s exceeds 0.1, 0.2, 0.5, 0.8, or 0.9.

An additional aspect of the invention relates to a pharmaceuticalcomposition comprising a particle of the invention, e.g., one or moreparticles as described herein and/or having one or more of the qualitiesdescribed above. In certain embodiments, the pharmaceutical compositionis adapted for topical delivery to a mucosal tissue in a patient. Theinvention further relates to a method for treating, preventing, ordiagnosing a condition in a patient, comprising administering to thepatient said pharmaceutical composition. Said pharmaceutical compositionmay be delivered to a mucosal surface in a patient, may pass through amucosal barrier in the patient, and/or may exhibit prolonged residencetime on a mucus-coated tissue, e.g., due to reduced mucoadhesion. Incertain embodiments, polymeric particles described herein, with orwithout a bioactive agent, can be administered to a patient, e.g., totreat, inhibit, or prevent a viral infection.

In certain embodiments, the invention provides a composition comprisinga plurality of particles, wherein at least 1%, 2%, 5%, 10%, 15%, 20%,30%, 40%, 50%, 70%, 90%, 95%, or even at least 99% of the totalparticles in the composition have one or more of the characteristicsdescribed in the preceding paragraphs. In addition, the inventionprovides a composition comprising a mixture of two or more types ofparticles, e.g., one of which types comprises particles that have one ormore of the characteristics described in the preceding paragraphs.

In one aspect, a particle comprises a pharmaceutically acceptablepolymer core and a surface-altering agent that is embedded or enmeshedin the particle's surface or that is disposed (e.g., by coating,adsorption, covalent linkage, or other process) on the surface of theparticle. The surface-altering agent may be a bioactive agent itself.For example, in certain embodiments, a particle may comprise apharmaceutically acceptable polymer and a nucleic acid coating thesurface of the particle. In such embodiments, the nucleic acid moleculemay alter the surface of the particle and make it mucus-resistant. Incertain other embodiments, a particle comprises a pharmaceuticallyacceptable polymer and a protein (e.g., serum albumin) disposed on thesurface of the particle. The protein may alter the surface of theparticle and make it mucus-resistant.

In any of the above embodiments, the particle may comprise a therapeuticagent or an imaging agent, e.g., that may include a diagnostic agentand/or a detectable label. For example, a nucleic acid or proteinincluded in the particle may comprise an imaging agent itself, e.g., adetectable label can be attached to the DNA or the protein.Alternatively, the particle may comprise an imaging agent that isseparate from the nucleic acid or the protein, e.g., encapsulated in thecore or disposed on or coupled to the surface. Additionally, theparticle may comprise one or more targeting moieties or moleculescoupled to the particle and/or the protein or nucleic acid, and thetargeting moiety can help deliver the nucleic acid, the protein, and/orthe therapeutic, imaging, and/or diagnostic agent to a targeted locationin a patient.

In certain embodiments, a particle comprises a pharmaceuticallyacceptable polymer core, a bioactive agent (e.g., a drug or medicament)encapsulated in the core, and a surface-altering agent that is embeddedor enmeshed in the particle's surface, or disposed (e.g., by coating,adsorption, covalent linkage, or other process) on the surface of theparticle and that alters the surface of the particle, e.g., to make itable to diffuse rapidly through mucus. The particle may comprise animaging agent, e.g., a diagnostic agent and/or a detectable label. Theencapsulated bioactive agent may be or comprise an imaging agent itself,e.g., a detectable label may be attached to a therapeutic agent.Alternatively, the particle may comprise an imaging agent that isseparate from the bioactive agent. Additionally, the particle maycomprise a targeting moiety or molecule coupled to the particle, and thetargeting moiety can help deliver the bioactive agent and/or the imagingagent to a desirable location in a patient.

In one aspect, a particle comprises a core having one more morebioactive agents (e.g., a drug or medicament) and a surface-alteringagent that is embedded or enmeshed in the particle's surface or that isdisposed (e.g., by coating, adsorption, covalent linkage, or otherprocess) on the surface of the particle. The surface-altering agent maybe a bioactive agent itself.

Alternatively, a particle may comprise a pharmaceutically acceptablepolymer core, a surface-altering agent, e.g., a surfactant, that isembedded or enmeshed in the particle's surface, or disposed (e.g., bycoating, adsorption, covalent linkage, or other process) on the surfaceof the particle and that alters the surface of the particle, such as bymaking it mucus-resistant, and a bioactive agent disposed on thepolymeric particle. The bioactive agent may be coated or otherwisedisposed on the surface of the particle, or be coupled to the particle,e.g., by covalent linkage, complexation, or other process. In certainsuch embodiments, the surface-altering agent is selected to promoteadhesion or complexation of the bioactive agent to the surface of theparticle. In such embodiments, the surface-altering agent and/or thebioactive agent may contribute to rapid diffusibility through mucus ofthe modified particles. The particles may comprise an imaging agent,such as a diagnostic agent and/or a detectable label. The bioactiveagent coated or disposed on the surface of the particle or coupled tothe particle may be or comprise an imaging agent itself, e.g., adetectable label can be attached to a therapeutic agent. Alternatively,the particle may comprise an imaging agent that is separate from thebioactive agent, e.g., encapsulated in the core or disposed on orcoupled to its surface. Additionally, the particle may comprise atargeting moiety or molecule coupled to the particle, and the targetingmoiety can help deliver the bioactive agent and/or the imaging agent toa targeted location in a patient.

The present invention also provides a particle, comprising a polymerhaving regions of polyethylene glycol or its derivatives that arepresented on the surface of the particle. The particle may optionallycomprise an additional surface-altering agent. The particle may furthercomprise a bioactive agent and/or a targeting moiety.

Bioactive agents according to the invention include but are not limitedto a nucleic acid, DNA (e.g., a gene therapy vector or plasmid), an RNA(e.g., an mRNA, the transcript of an RNAi construct, or an siRNA), asmall molecule, a peptidomimetic, a protein, peptide, lipid, surfactantand combinations thereof.

The surface-altering agent may alter the charge or increase thehydrophilicity of the particle, or otherwise promote motility throughmucus. The surface-altering agent may enhance the average rate at whichthe particles, or a fraction of the particles, move in or through mucus.Examples of suitable surface-altering agents include but are not limitedto anionic protein (e.g., serum albumin), nucleic acids, surfactantssuch as cationic surfactants (e.g., dimethyldioctadecyl-ammoniumbromide), sugars or sugar derivatives (e.g., cyclodextrin), polyethyleneglycol, mucolytic agents, or other non-mucoadhesive agents. A preferredembodiment comprises polyethylene glycol covalently linked to theparticle core. Certain agents, e.g., cyclodextrin, may form inclusioncomplexes with other molecules and can be used to form attachments toadditional moieties and facilitate the functionalization of the particlesurface and/or the attached molecules or moieties. Examples of suitablecarbohydrate surface-altering agents include agar, agarose, alginicacid, amylopectin, amylose, beta-glucan, callose, carrageenan,cellodextrins, cellulin, cellulose, chitin, chitosan, chrysolaminarin,curdlan, cyclodextrin, dextrin, ficoll, fructan, fucoidan,galactomannan, gellan gum, glucan, glucomannan, glycocalyx, glycogen,hemicellulose, hydroxyethyl starch, kefiran, laminarin, mucilage,glycosaminoglycan, natural gum, paramylon, pectin, polysaccharidepeptide, schizophyllan, sialyl lewis x, starch, starch gelatinization,sugammadex, xanthan gum, and xyloglucan, as well as fragments andderivatives of such carbohydrates.

The particles of the invention have many applications. In particular,they are well-suited for making pharmaceutical compositions,particularly those for which the route of administration involves theparticles passing through a mucosal barrier. For example, the particlesare particularly suitable for making pharmaceutical compositions to beformulated as nasal spray, such that the pharmaceutical compositions canbe delivered across a nasal mucus layer. In addition, the particles areparticularly suitable for making pharmaceutical compositions to beformulated as an inhaler, such that the pharmaceutical compositions canbe delivered across a pulmonary mucus layer. Similarly, the particlesare particularly suitable for making pharmaceutical compositions fordelivery via gastrointestinal, respiratory, rectal, and/or vaginaltissues.

A pharmaceutically acceptable polymer may be apoly(D,L-lactic-co-glycolic) acid, polyethylenimine,dioleyltrimethyammoniumpropane/dioleyl-sn-glycerolphosphoethanolamine,polysebacic anhydride, or other polymer formed from clinicallyacceptable or approved monomers. Examples of clinically approvedmonomers include but are not limited to monomers of sebacic acid and3-bis(carboxyphenoxy)propane. Other polymers or copolymers describedherein can also be employed to make the polymeric particles of theinvention.

In certain embodiments, a bioactive agent is a therapeutic agent or animaging agent (e.g., a diagnostic agent). Examples of therapeutic agentsinclude but are not limited to a nucleic acid, a nucleic acid analog, asmall molecule, a peptidomimetic, a protein, peptide, lipid, orsurfactant, and combinations thereof. In certain embodiments, theimaging agent further comprises a detectable label.

In certain embodiments, a particle of the invention may further comprisea targeting agent or molecule. A particle may also further oralternatively comprise an adjuvant.

In certain embodiments, a particle of the invention may further comprisean agent covalently linked to the particle. The agent may be a bioactiveagent, such as a drug. The agent may preferably be a hydrophilic agent,such that through its covalent linkage to the particle, the agent alterscharge or hydrophilicity of the particle, e.g., to decrease theparticle's mucoadhesion. The covalent linkage may be cleavable underbiological conditions.

Also provided is an inhaler or nebulizer comprising a particle asdescribed herein.

An additional aspect relates to a use of a particle as described hereinin the manufacture of a medicament for the treatment, prevention, ordiagnosis of a condition in a patient, including medicaments adapted fortopical administration to a mucosal tissue.

An additional aspect relates to a method for transfecting a cellcomprising contacting the cell with a particle of the invention thatcomprises a nucleic acid. A particle of the invention comprising anucleic acid may transfect a cell at a higher efficiency, e.g., at 2, 5,10, 20, 50, 100 or greater-fold higher efficiency, than the nakednucleic acid, e.g., in the presence of a mucosal barrier.

An additional aspect related to a method for treating, preventing, ordiagnosing a condition in a patient, comprising administering to thepatient a particle as described herein or a pharmaceutical compositioncomprising one or more such particles, e.g., by topical administrationto a mucosal tissue. In certain embodiments, the particle passes througha mucosal barrier in the patient.

An exemplary method for preparing such particles may include: providingmicroparticles or nanoparticles comprising a pharmaceutically acceptablepolymer and coupling (e.g., by coating, covalent linkage, orco-localization) to the surface of the microparticles or nanoparticles asurface-altering agent, e.g., a polyethylene glycol, a nucleic acid, aprotein, or a carbohydrate. Such a method may further include: coupling(e.g., by coating, covalent linkage, or co-localization) to theparticles an imaging agent, a detectable label, or a targeting moiety.The method may further include one or more of: forming a particlesuspension, passing the particle suspension through a filter, removingimpurities from the particle suspension, centrifugation to pellet theparticles, dialyzing the particle suspension, and adjusting the pH ofthe particle suspension. The method may also include quenching thecovalent linking reaction.

An additional aspect of the invention comprises a method of reducing themucoadhesiveness of a substance by modifying the substance with asurface-altering moiety, such as PEG or a carbohydrate. Herein, theterms “surface-altering moiety” and “surface-altering agent” are usedsubstantially interchangeably, wherein “surface-altering agent” referespreferentially to an individual entity and “surface-altering moiety”refers to all or part of a molecule. The surface-altering moiety mayenhance the hydrophilicity of the substance. For example, in certainembodiments, the invention comprises identifying a therapeutic agent orparticle, e.g., small molecule, nucleic acid, protein, liposome,polymer, liposome, virus (e.g. an enveloped virus or capsid virus),metal, or metal oxide, the mucoadhesiveness of which is desired to bereduced. The substance may then be modified with a surface-alteringagent. For example, the method may comprise identifying a moiety on thesubstance (e.g., small molecule, protein, liposome, polymer, liposome,or virus) to which the surface-altering agent (e.g., PEG) may becovalently attached, e.g., without losing activity, or through a bondsusceptible to intracellular cleavage (e.g., hydrolytic or enzymatic),such as an ester or amide. Alternatively, the surface-altering agent maybe non-covalently associated with the substance, e.g., by coating aparticulate form of the substance, e.g., to promote its diffusivitythrough mucus. In certain embodiments, the method further comprisesformulating a pharmaceutical preparation of the modified substance,e.g., in a formulation adapted for topical delivery to a mucosal tissueof a patient. The formulation may be administered to a patient.

An additional aspect of the invention comprises a method of increasingthe diffusivity in mucus of a substance in need thereof, by modifyingthe substance with a surface-altering agent. For example, in certainembodiments the invention comprises selecting a substance in need ofincreased diffusivity through mucus, an appropriate surface-alteringagent to promote diffusion of the substance through mucus, and a moietyon said substance to which the surface-altering agent may be coupled inorder to increase the substance's diffusivity through mucus whileavoiding the total loss of activity of the substance. Thesurface-altering agent may then be disposed on said substance, in orderto increase its diffusivity through mucus. In addition, the substancewith said surface-altering agent may be formulated to produce apharmaceutical preparation, which may be delivered to a patient with thepurpose of increasing diffusivity in mucus, e.g., in a formulationadapted for topical delivery to a mucosal tissue of a patient. Saidpharmaceutical preparation or the substance with said surface-alteringagent may be delivered to a mucosal surface in a patient, may passthrough a mucosal barrier in the patient, and/or may exhibit prolongedresidence time on a mucus-coated tissue, e.g., due to reducedmucoadhesion.

Substances in need of increased diffusivity may, for example, behydrophobic, have many hydrogen bond donors or acceptors, or be highlycharged. Such a substance may be an agent that travels through humanmucus at less than or equal to one-tenth (or even one-hundredth orone-thousandth) the rate it travels through water. A number of drugsthat are mucoadhesive are known in the art (Khanvilkar K, Donovan M D,Flanagan D R, Drug transfer through mucus, Advanced Drug DeliveryReviews 48 (2001) 173-193; Bhat P G, Flanagan D R, Donovan M D. Drugdiffusion through cystic fibrotic mucus: steady-state permeation,rheologic properties, and glycoprotein morphology, J Pharm Sci, 1996June; 85(6):624-30). As an example, dexamethasone, a corticosteriod fortreating inflammation, is suggested to not be efficient because ofinadequate penetration of the mucus barrier (Kennedy, M. J.,Pharmacotherapy, 2001, 21(5): p. 593-603). In addition, mucus slows thediffusion of some proteins; see, for example Saltzman W M, Radomsky M L,Whaley K J, Cone R A, Antibody Diffusion in Human Cervical Mucus,Biophysical Journal, 1994, 66:508-515.

In certain embodiments, substances (such as particles) modified withsurface-altering agents as described herein may pass through a mucosalbarrier in the patient, and/or exhibit prolonged residence time on amucus-covered tissue, e.g., such substances are cleared more slowly(e.g., at least 2 times, 5 times, 10 times, or even at least 20 timesmore slowly) from a patient's body than a typical comparablecarboxyl-modified polystyrene particle.

The present invention also contemplates the use of “sacrificial”particles or polymers to promote transport of active particles throughmucus, wherein sacrificial particles or polymers increase the rate atwhich the active particles move through the mucus. Without wishing to bebound by theory, it is believed that such sacrificial particles interactwith the mucus and alter either the structural or adhesive properties ofthe surrounding mucus such that the active particles experiencedecreased mucoadhesion. For example, the invention contemplates the useof PEG (e.g., not physically or chemically associated with the activeparticle(s)) as a sacrificial polymer to promote the diffusion ofcertain particles through mucus. In addition, the invention contemplatesthe use of particles lacking a surface-altering agent (and optionallylacking a therapeutic agent), used in combination with surface-alteringparticles of the invention, e.g., containing a therapeutic agent. Incertain embodiments, sacrificial particles are carboxyl-modifiedpolystyrene (PS) particles. In certain embodiments, the inventioncontemplates use of sacrificial particles which are less than 1,000,000,500,000, 200,000, 100,000, 50,000, 20,000, 10,000, 5000, 2000, 1000,500, 200, 100, 50, 20, 10, 5, 2, or 1 nm in diameter, or have a diameterintermediate between arty of these values. In certain embodiments, theinvention contemplates use of sacrificial particles that pass through amucosal barrier at a rate that is less than 1/100 1/200, 1/500, 1/600,1/1000, 1/2000, 1/3000, 1/5000, or even less than 1/10,000 of the rateof the particle in water under identical conditions. Further, thepresent invention provides sacrificial particles that travel at certainabsolute rates. For example, the sacrificial particles may travel atrates less than 2, 1, 5×10⁻¹, 2×10⁻¹, 1×10⁻¹, 8×10⁻², 6×10⁻², 5×10⁻²,4×10⁻², 2×10⁻², 1×10⁻², 5×10⁻³, 2×10⁻³, 1×10⁻³, 5×10⁻⁴, 2×10⁻⁴, 1×10⁻⁴,5×10⁻⁵, 2×10⁻⁵, or even less than 1×10⁻⁵ μm²/s, at a time scale of 1 s.

The present invention also contemplates a composition of matter whichcomprises human mucus (e.g., cervicovaginal, pulmonary,gastrointestinal, nasal, respiratory, or rectal mucus) and any of theparticles described above.

The present invention also contemplates a particle comprising a polymerthat includes regions of a surface-altering agent that localize to thesurface of the particle. For example, a particle may be a copolymer of amucoresistant polymer, such as PEG. Such a polymer may form a particlewherein regions that promote diffusion through mucus, are localized onthe surface of the particle, thus reducing or even obviating the needfor a separate coating or other modification with a surface-alteringagent.

In certain embodiments, a particle may include an agent that promotesdiffusion through mucus, wherein said agent is present both on thesurface and inside the particle. Said agent may be attached covalentlyor noncovalently to another component of the particle such as abioactive agent or a polymeric vehicle.

The invention further provides a composition comprising a firstplurality of particles and a second plurality of particles. In certainembodiments, the first plurality of particles and the second pluralityof particles are distinct types of particles. In certain embodiments,the first plurality of particles comprises mucoresistant particles asdescribed above and the second plurality comprises sacrificialparticles. In certain embodiments, the first plurality of particles makeup at least 1%, 2%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 70%, 90%, 95%, or99% of the total particles in the composition. In certain embodiments,the second plurality of particles make up at least 1%, 2%, 5%, 10%, 15%,20%, 30%, 40%, 50%, 70%, 90%, 95%, or 99% of the total particles in thecomposition. In certain embodiments, the particles of the firstplurality have one or more of the characteristics described in thepreceding paragraphs.

Particles within a plurality of particles may be classified as havingone of three modes of transport; diffusive, immobile, and hindered.

In certain embodiments, the second plurality of particles comprises animmobile fraction defined as those those that display an average MSDsmaller than the 10-nm resolution at a time scale of 1 s. In certainembodiments, the immobile fraction may comprise greater than 80%, 70%,60%, 50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of the particles in thesecond plurality.

In certain embodiments, the second plurality of particles comprises ahindered fraction which strongly adheres to mucus but is not immobile.The sum of the hindered and immobile fractions is defined herein inSection 1.5 of the Exemplification as particles, that display RC valuesbelow the 97.5% range for either short or long time scales. In certainembodiments, the hindered fraction may comprise greater than 85%, 60%,50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of the particles in the secondplurality. The second plurality of particles may diffuse through humancervicovaginal mucus at an average diffusivity that is less than 1/100,1/200, 1/500, 1/1000, 1/2000, 1/5000, or 1/10000 the diffusivity thatthe particles diffuse through water at a time scale of 1 s.

In certain embodiments, the first plurality of particles comprises adiffusive fraction which adheres weakly to mucus or does not adhere atall. The diffusive fraction is defined herein in Section 1.5 of theExemplification as particles that are not hindered or immobile. Incertain embodiments, the particles of the diffusive fraction have one ormore of the mucus-resistant qualities discussed above. In certainembodiments, the diffusive fraction may comprise greater than 85%, 60%,50%, 40%, 30%, 20%, 10%, 5%, 2%, or 1% of the particles in the firstplurality.

Another aspect of the invention provides an envelope virus having asurface-altering moiety disposed on a surface of the virus (e.g.,coating the surface of the virus), wherein said virus diffuses throughhuman cervicovaginal mucus at a diffusivity (at a time scale of 1 s)that is more than 5, 10, 20, 50, 100, 200, 500, or 1000-fold greaterthan the diffusivity at which a corresponding virus lacking thesurface-altering moiety diffuses through human cervicovaginal mucus. Thevirus may further comprise a vector or other therapeutic nucleic acid ascontemplated herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C. Transport rates of COOH-modified polystyrene(COOH-PS) particles in CV mucus. (A) Ensemble-averaged geometric meansquare displacements (<MSD>) and (B) effective diffusivities (<D_(eff)>)as a function of time scale. (C) Average D_(eff) of sub-fractions ofparticles, from fastest to slowest, at a time scale of Is. “W” indicatesthe D_(eff) in pure water. The dashed black line at <D_(eff)>=1×10⁻⁴signifies the microscope's resolution—particles slower than this valueare considered immobile. Data represent average of 3 experiments, withn≥120 particles for each experiment.

FIGS. 2A, 2B, 2C, 2D, 2E, and 2F. Transport rates of polystyreneparticles modified with 2 kDa PEG (PEG2 kDa-PS) in CV mucus. (A)Ensemble-averaged geometric mean square displacements (<MSD>) and (B)effective diffusivities (<D_(eff)>) as a function of time scale. (C)Average D_(eff) of sub-fractions of PEG2 kDa-PS, from fastest toslowest, at a time scale of 1 s. The dashed black line at<D_(eff)>=1×10-4 signifies the microscope's resolution—particles slowerthan this value are considered immobile. Transport mode distributions ofCOOH-PS and PEG2 kDa-PS: (D) immobile particles, (E) immobile andhindered particles, and (F) diffusive particles. Data represent ensembleaverage of three experiments, with n≥120 particles for each experiment.

FIGS. 3A and 3B. Transport rates of polystyrene particles modified with10 kDa PEG (PEG10 kDa-PS) in CV mucus. (A) Ensemble-averaged geometricmean square displacements (<MSD>) as a function of time scale. (B)Fractions of PEG10 kDa-PS undergoing different transport modes: immobile(Imm), immobile and hindered (I+H), and diffusive (Diff) particles. Datarepresent ensemble average of three experiments, with n≥110 particlesfor each experiment.

FIGS. 4A, 4B, 4C, 4D and 4E. Effect of mucolytics (rhDNase, NAC) onmucus rheology and particle transport in CF mucus. MSDs of a subset ofindividual 200 nm particles for (A) no treatment (notice largevariation) and (B) pulmozyme (rhDNAse) treatment (notice more uniform)(n≥120). (C) Bulk viscosity was reduced ˜50% by treatment with rhDNase,but surprisingly did not correlate to improved particle transport in CFmucus (D) (see our paper in JBC for explanation [19]). Particletransport in CF mucus was dramatically improved, however, with NAC: (E)Effective diffusivities of 100 nm particles (n=100-180) was increasedsignificantly (p<0.05) at 30 mins (0.4 mM NAC).

FIGS. 5A and 5B. Ensemble averaged transport rates of PEG-modified 500nm polystyrene (PEG-PS) nanoparticles in undiluted lung mucusexpectorated from cystic fibrosis (CF) patients. (A) Ensemble geometricmean square displacements show that pretreatment of mucus withneutralized N-acetyl-L-cysteine increased transport rates 10.7-foldcompared to no treatment control (PBS). (B) Classifying the trajectoriesof particle motion into different transport modes (immobile, hindered,diffusive) show that the diffusive fraction of 500 nm PEG-PS is enhanced3-fold compared to the no treatment control. For both conditions, thenumber of immobile particles is <3%. Data represent n=200-250 particlesper condition.

FIGS. 6A, 6B, and 6C. Typical trajectories of particles undergoingtransport in CV mucus: (A) immobile, (B) hindered, and (C) diffusiveparticles. Scale bar represents 2.3 μm for all trajectories. Inset showsmotions of immobile particle zoomed in 1000×; scale bar in Insetrepresents 2.3 nm.

FIGS. 7A and 7B. (A) Surface density of polyethylene glycol (PEG; M.W.˜3.4 kDa) on two different particle preparations. Prep A: PEG adsorbedon to 500 nm polystyrene particles as disclosed in Example 6B in WO2005/072710 A2, Prep B: High density PEG conjugated to 500 nmpolystyrene particles as described in Lai et al, PNAS v104(5):1482-1487. (B) Mass ratio of core polymer to surface PEG for Prep A andPrep B.

FIG. 8 . Table depicting size of particles (column 1), surface chemistryof particles (COOH uncoated, PEG=coated) (column 2), experimentallydetermined diameter of particles (column 3), zeta-potential of particles(column 4), avidin adsorbance of particles (column 5), and effectivediffusivity at a time scale of 1 s (column 5).

DETAILED DESCRIPTION OF THE INVENTION 1. Overview

The present invention relates in part to a nanoparticle or microparticlecoated with a surface agent that facilitates passage of the particlethrough mucus. Said nanoparticles and microparticles have a higherconcentration of surface agent than has been previously achieved,leading to the unexpected property of extremely fast diffusion throughmucus. The present invention further comprises a method of producingsaid particles. The present invention further comprises methods of usingsaid particles to treat a patient.

Cervicovaginal (CV) mucus typically exhibits macroscopic viscositywithin the range (albeit in the higher end) of typical human mucussecretions, including lungs, GI tract, nose, eyes and epididymus. Thisis partly attributed to the similarity in the chemical composition ofvarious human mucuses. For example, the mucin glycoform MUC5B is themajor secreted form of mucin in the mucosal layers protecting the CVtract, lungs, nose, and eye. The mucin content, approximately 1-3% byweight, is also similar between cervical, nasal and lung mucus. Thecomposition of water in the aforementioned mucus types all falls withinthe range of 90-98%. The similar mucus composition and mucin glycoformslead to similar rheology, characterized here by log-linearshear-thinning of viscosity.

Nanoparticles larger than the reported average mesh pore size of humanmucus (approximately 100 nm) have been thought to be much too large toundergo rapid diffusional transport through mucus barriers. However,large nanoparticles are preferred for higher drug encapsulationefficiency and the ability to provide sustained delivery of a widerarray of drugs. We disclose herein a new composition of mattercomprising large nanoparticles, 500 and 200 nm in diameter, coated witha surface-modifying agent, such as polyethylene glycol. Suchnanoparticles diffuse through mucus with an effective diffusioncoefficient (D_(eff)) nearly as high as that for the same particles inwater (at timescale τ=1 s). In contrast, for uncoated particles 100-500nm in diameter, D_(eff) was 2400- to 40,000-fold lower in mucus than inwater. Thus, in contrast to the prevailing belief, these resultsdemonstrate that large nanoparticles, if properly coated, can rapidlypenetrate physiological human mucus, and offer the prospect that largenanoparticles can be used for mucosal drug delivery.

Treatments for cervicovaginal (CV) tract diseases, often based on drugsdelivered to the systemic circulation via pills or injections, typicallysuffer from low efficacy. For example, systemic chemotherapy istypically the last or strictly concurrent option, after surgery andradiotherapy, for treatment of cervical cancer. In addition, systemicmedications can lead to significant adverse side effects, when high drugconcentrations in the circulation are required to elicit a therapeuticresponse in the CV tract. To reduce side effects and achieve localizedtherapy, recent efforts have increasingly emphasized topical drugdelivery methods, such as creams, hydrogels, and inserted devices, todeliver therapeutics via the apical side of the cervix epithelium.Apical drug delivery may also be extended to protection against sexualtransmission of infections, since neutralizing antibodies andmicrobicides must act at mucosal surfaces in order to block the entry ofpathogens.

Nanoparticle systems possess desirable features for treatment,including: (i) sustained and controlled release of drugs locally, (ii)potential to cross the mucosal barrier due to the nano-metric size,(iii) rapid intracellular trafficking to the perinuclear region ofunderlying cells, and (iv) protection of cargo therapeutics fromdegradation and removal in the mucus. However, therapeutic and/ordiagnostic particles must overcome the mucosal barrier lining thecervicovaginal tract in order to reach underlying cells and avoidclearance. Mucins, highly glycosylated large proteins (10-40 MDa)secreted by epithelial cells, represent the principle component of theentangled viscoelastic gel that protects the underlying epithelia fromentry of pathogens and toxins. Other mucus constituents, such as lipids,salts, macromolecules, cellular debris and water, work together withmucins to form a nanoscopically heterogeneous environment fornanoparticle transport, where the shear-dependent bulk viscosity istypically 100-10,000 times more viscous than water. Small viruses up to55 nm have been shown to diffuse in CV mucus as rapidly as in water,however, a larger virus, 180 nm herpes simplex virus, was slowed 100- to1000-fold by CV mucus compared to water, suggesting that the mucus meshspacing is about 20-200 nm. It was also previously reported thatpolystyrene particles (59-1000 nm) adhered tightly to cervical mucus,rendering them completely immobile (Olmsted, S S, Padgett, J L, Yudin, AI, Whaley, K J, Moench, T R & Cone, R A (2001) Biophysical Journal 81,1930-1937, incorporated herein by reference). These observations havesuggested that the transport of synthetic polymer nanoparticles,especially those larger than ˜59 nm, was unlikely to occur efficientlyenough to allow access of sustained release particles to underlyingepithelium in human mucus-covered tissues.

To investigate and potentially improve the transport of nanoparticlesacross the cervicovaginal mucus barrier, we studied the quantitativetransport rates of hundreds of individual nanoparticles of various sizesand surface chemistries in human cervicovaginal secretions. Undilutedmucus at physiologically relevant conditions was obtained by a novelprocedure that uses a menstrual collection device (Boskey, ER, Moench, TR, 0, P S & Cone, RA (2003) Sexually Transmitted Diseases 30, 107-109,incorporated herein by reference). Surprisingly, we report thatnanoparticles, including those larger than the previously reported CVmucus mesh spacing, are capable of rapid transport in CV mucus if theyare coated with a muco-resistant polymer, such as polyethylene glycol.

High MW poly(ethylene glycol) (PEG) has been used as a mucoadhesiveadded to polymeric systems for its reported ability to interpenetrateinto the mucus network (Bures et al., J. Controlled Release, (2001)72:25-33; Huang et al., J. Controlled Release, (2000) 65:63-71; Peppaset al., 3. Controlled Release, (1999) 62:81-87, all of which areincorporated by reference herein in their entirety) and hydrogen bond tomucins Willits et al., Biomaterials, (2001) 22:445-452; Sanders et al.,J. Controlled Release, (2003) 87:117-129, and PCT Patent Application No.US2005/002556, all of which are incorporated herein by reference intheir entirety). However, as shown in the examples below, modifying thesurface of different particle types having a dense PEG coating decreasedthe adsorption of mucus components to the particle surface and allowedmore rapid transport through mucus with a reduced number of adhesiveparticles. High MW poly(ethylene glycol) may be employed to reducemucoadhesion in certain configurations, e.g., wherein the length of PEGchains extending from the surface is controlled (such that long,unbranched chains that interpenetrate into the mucus network are reducedor eliminated). For example, linear high MW PEG may be employed in thepreparation of particles such that only portions of the linear strandsextend from the surface of the particles (e.g., portions equivalent inlength to lower MW PEG molecules). Alternatively, branched high MW PEGmay be employed. In such embodiments, although the molecular weight of aPEG molecule may be high, the linear length of any individual strand ofthe molecule that extends from the surface of a particle wouldcorrespond to a linear chain of a lower MW PEG molecule.

PEG can be produced in a range of molecular weights. The presentinvention contemplates the use of one or more different molecularweights of PEG on the surface of nanoparticles, including but notlimited to 300 Da, 600 Da, 1 kDa, 2 kDa, 3 kDa, 4 kDa, 6 kDa, 8 kDa, 10kDa, 15 kDa, 20 kDa, 30 kDa, 50 kDa, 100 kDa, 200 kDa, 500 kDa, and 1MDa. In addition, PEG of any given molecular weight may vary in othercharacteristics such as length, density, and branching. This inventioncontemplates the use of different variants of PEG, including PEG ofdifferent lengths, densities, or branchedness.

While not wishing to be bound by theory, one possible mechanism for thiseffect is that PEG alters the microenvironment of the particle, forexample by ordering water and other molecules in the particle/mucusenvironment; an additional or alternative possible mechanism is thatfree PEG shields the adhesive domains of the mucin fibers, therebyreducing particle adhesion and speeding up particle transport.

Modification of particle surface with other polymers, proteins,surfactants, sugars, carbohydrates, nucleic acids, or non-mucoadhesivematerials may also result in increased transport in mucus and otheradhesive biological fluids, such as serum. In certain embodiments, theparticle surface is coated with one or more of DNA, RNA, bovine serumalbumin (BSA), human serum albumin (HSA), poly-glycine, polyglycolicacid, agar, agarose, alginic acid, amylopectin, amylose, beta-glucan,callose, carrageenan, cellodextrins, cellulin, cellulose, chitin,chitosan, chrysolaminarin, curdlan, cyclodextrin, dextrin, ficoll,fructan, fucoidan, galactomannan, gellan gum, glucan, glucomannan,glycocalyx, glycogen, hemicellulose, hydroxyethyl starch, kefiran,laminarin, mucilage, glycosaminoglycan, natural gum, paramylon, pectin,polysaccharide peptide, schizophyllan, sialyl lewis x, starch, starchgelatinization, sugammadex, xanthan gum, and xyloglucan. For example, asshown below, modification of particle surface by the covalent attachmentof PEG to COOH-modified particles increases transport in mucus.Furthermore, addition of N-Acetyl Cysteine increases transport in mucus.Other molecules such as surfactants or polymers, including poly(asparticacid), and proteins, such as heparin, may also increase transport ratesin mucus.

Accordingly, the present invention relates to particles (for example,polymeric or liposomal particles) and compositions comprising them, suchas pharmaceutical compositions for the delivery of biologically activeand/or therapeutic agents, e.g., for the prevention, detection ortreatment of a disease or other condition in a patient, particularly,for delivery across mucosal barriers in the patient. The presentinvention also provides a particle comprising a polymer having regionsof polyethylene glycol that are presented on the surface of theparticle. In certain embodiments, biodegradable and/or biocompatiblepolymers may be used to transport or carry an adsorbed or encapsulatedtherapeutic agent across a mucosal barrier present in any mucosalsurface, e.g., gastrointestinal, nasal, respiratory, rectal, or vaginalmucosal tissues in a patient. Agents that may be adsorbed orencapsulated in the subject compositions include imaging and diagnosticagents (such as radioopaque agents, labeled antibodies, labeled nucleicacid probes, dyes, such as colored or fluorescent dyes, etc.) andadjuvants (radiosensitizers, transfection-enhancing agents, chemotacticagents and chemoattractants, peptides that modulate cell adhesion and/orcell mobility, cell permeabilizing agents, vaccine potentiators,inhibitors of multidrug resistance and/or efflux pumps, etc.). Thepresent invention also relates to methods of making and/or administeringsuch compositions, e.g., as part of a treatment regimen, for example, byinhalation, topically (e.g., for administration to a mucosal tissue of apatient), or by injection, e.g., subcutaneously, intramuscularly, orintravenously.

2. Definitions

For convenience, before further description of the present invention,certain terms employed in the specification, examples, and appendedclaims are collected here. These definitions should be read in light ofthe remainder of the disclosure and understood as by a person of skillin the art.

The term “access device” is an art-recognized term and includes anymedical device adapted for gaining or maintaining access to an anatomicarea. Such devices are familiar to artisans in the medical and surgicalfields. An access device may be a needle, a catheter, a cannula, atrocar, a tubing, a shunt, a drain, or an endoscope such as an otoscope,nasopharyngoscope, bronchoscope, or any other endoscope adapted for usein the head and neck area, or any other medical device suitable forentering or remaining positioned within the preselected anatomic area.

The terms “biocompatible polymer” and “biocompatibility” when used inrelation to polymers are art-recognized. For example, biocompatiblepolymers include polymers that are neither themselves toxic to the host(e.g., an animal or human), nor degrade (if the polymer degrades) at arate that produces monomeric or oligomeric subunits or other byproductsat toxic concentrations in the host. In certain embodiments of thepresent invention, biodegradation generally involves degradation of thepolymer in an organism, e.g., into its monomeric subunits, which may beknown to be effectively non-toxic. Intermediate oligomeric productsresulting from such degradation may have different toxicologicalproperties, however, or biodegradation may involve oxidation or otherbiochemical reactions that generate molecules other than monomericsubunits of the polymer. Consequently, in certain embodiments,toxicology of a biodegradable polymer intended for in vivo use, such asimplantation or injection into a patient, may be determined after one ormore toxicity analyses. It is not necessary that any subject compositionhave a purity of 100% to be deemed biocompatible. Hence, a subjectcomposition may comprise 99%, 98%, 97%, 96%, 95%, 90% 85%, 80%, 75% oreven less of biocompatible polymers, e.g., including polymers and othermaterials and excipients described herein, and still be biocompatible.

To determine whether a polymer or other material is biocompatible, itmay be necessary to conduct a toxicity analysis. Such assays are wellknown in the art. One example of such an assay may be performed withlive carcinoma cells, such as GT3TKB tumor cells, in the followingmanner: the sample is degraded in 1 M NaOH at 37° C. until completedegradation is observed. The solution is then neutralized with 1 μM HCl.About 200 μL of various concentrations of the degraded sample productsare placed in 96-well tissue culture plates and seeded with humangastric carcinoma cells (GT3TKB) at 10⁴/well density. The degradedsample products are incubated with the GT3TKB cells for 48 hours. Theresults of the assay may be plotted as % relative growth vs.concentration of degraded sample in the tissue-culture well. Inaddition, polymers and formulations of the present invention may also beevaluated by well-known in vivo tests, such as subcutaneousimplantations in rats to confirm that they do not cause significantlevels of irritation or inflammation at the subcutaneous implantationsites.

Exemplary biocompatible and biodegradable polymers disclosed in U.S.Pat. No. 7,163,697, herein incorporated by reference, may be employed tomake the polymeric particles of the present invention.

The term “biodegradable” is art-recognized, and includes polymers,compositions and formulations, such as those described herein, that areintended to degrade during use. Biodegradable polymers typically differfrom non-biodegradable polymers in that the former may degrade duringuse. In certain embodiments, such use involves in vivo use, such as invivo therapy, and in other certain embodiments, such use involves invitro use. In general, degradation attributable to biodegradabilityinvolves the degradation of a biodegradable polymer into its componentsubunits, or digestion, e.g., by a biochemical process, of the polymerinto smaller, non-polymeric subunits. In certain embodiments, twodifferent types of biodegradation may generally be identified. Forexample, one type of biodegradation may involve cleavage of bonds(whether covalent or otherwise) in the polymer backbone. In suchbiodegradation, monomers and oligomers typically result, and even moretypically, such biodegradation occurs by cleavage of a bond connectingone or more of subunits of a polymer. In contrast, another type ofbiodegradation may involve cleavage of a bond (whether covalent orotherwise) internal to sidechain or that connects a side chain to thepolymer backbone. For example, a therapeutic agent or other chemicalmoiety attached as a side chain to the polymer backbone may be releasedby biodegradation. In certain embodiments, one or the other or bothgeneral types of biodegradation may occur during use of a polymer.

As used herein, the term “biodegradation” encompasses both general typesof biodegradation. The degradation rate of a biodegradable polymer oftendepends in part on a variety of factors, including the chemical identityof the linkage responsible for any degradation, the molecular weight,crystallinity, biostability, and degree of cross-linking of suchpolymer, the physical characteristics (e.g., shape and size) of theimplant, and the mode and location of administration. For example, thegreater the molecular weight, the higher the degree of crystallinity,and/or the greater the biostability, the biodegradation of anybiodegradable polymer is usually slower. The term “biodegradable” isintended to cover materials and processes also termed “bioerodible.”

In certain embodiments wherein the biodegradable polymer also has atherapeutic agent or other material associated with it, thebiodegradation rate of such polymer may be characterized by a releaserate of such materials. In such circumstances, the biodegradation ratemay depend on not only the chemical identity and physicalcharacteristics of the polymer, but also on the identity of material(s)incorporated therein.

In certain embodiments, polymeric formulations of the present inventionbiodegrade within a period that is acceptable in the desiredapplication. In certain embodiments, such as in vivo therapy, suchdegradation occurs in a period usually less than about five years, oneyear, six months, three months, one month, fifteen days, five days,three days, or even one day or less (e.g., 4-8 hours) on exposure to aphysiological solution with a pH between 6 and 8 having a temperature ofbetween 25 and 37° C. In other embodiments, the polymer degrades in aperiod of between about one hour and several weeks, depending on thedesired application.

The term “cervicovaginal mucus” is art-recognized and refers to fresh,minimally diluted non-ovulatory cervicovaginal mucus collected from ahuman subject.

The term “corresponding particle” is used herein to refer to a particlethat is substantially identical to a particle to which it is compared,but typically lacking a mucoresistant surface modification. Acorresponding particle may be of similar material, density, and size asthe particle to which it is compared. In certain embodiments, acorresponding particle is a carboxyl-modified polystyrene (PS) particle,e.g., available from Molecular Probes, Eugene, Oreg. In certainembodiments, a comparable particle is a polystyrene particle that haseither carboxyl, amine or sulfate aldehyde surface modifications. Saidcarboxyl groups are preferably present at a density of 1.77 to 6.69carboxyls per nm². In certain embodiments, a corresponding particle ispolymeric, liposomal, viral, metal, metal oxide (e.g., silica), or aquantum dot that differs substantially only in a specified way, such asthe lack of a mucoresistant surface modification.

The term “DNA” is art-recognized and refers herein to a polymer ofdeoxynucleotides. Examples of DNA include plasmids, gene therapy vector,and a vector designed to induce RNAi.

The term “diameter” is art-recognized and is used herein to refer toeither of the physical diameter or the hydrodynamic diameter of theentity in question. The diameter of an essentially spherical particlemay refer to the physical or hydrodynamic diameter. The diameter of anonspherical particle may refer preferentially to the hydrodynamicdiameter. As used herein, the diameter of a non-spherical particle mayrefer to the largest linear distance between two points on the surfaceof the particle. When referring to multiple particles, the diameter ofthe particles typically refers to the average diameter of the particlesreferred to.

The term “drug delivery device” is an art-recognized term and refers toany medical device suitable for the application of a drug or therapeuticagent to a targeted organ or anatomic region. The term includes, withoutlimitation, those formulations of the compositions of the presentinvention that release the therapeutic agent into the surroundingtissues of an anatomic area. The term further includes those devicesthat transport or accomplish the instillation of the compositions of thepresent invention towards the targeted organ or anatomic area, even ifthe device itself is not formulated to include the composition. As anexample, a needle or a catheter through which the composition isinserted into an anatomic area or into a blood vessel or other structurerelated to the anatomic area is understood to be a drug delivery device.As a further example, a stent or a shunt or a catheter that has thecomposition included in its substance or coated on its surface isunderstood to be a drug delivery device.

When used with respect to a therapeutic agent or other material, theterm “sustained release” is art-recognized. For example, a subjectcomposition which releases a substance over time may exhibit sustainedrelease characteristics, in contrast to a bolus type administration inwhich the entire amount of the substance is made biologically availableat one time. For example, in particular embodiments, upon contact withbody fluids including blood, spinal fluid, mucus secretions, lymph orthe like, the polymer matrices (formulated as provided herein andotherwise as known to one of skill in the art) may undergo gradual ordelayed degradation (e.g., through hydrolysis) with concomitant releaseof any material incorporated therein, e.g., an therapeutic and/orbiologically active agent, for a sustained or extended period (ascompared to the release from a bolus). This release may result inprolonged delivery of therapeutically effective amounts of anyincorporated therapeutic agent.

The term “delivery agent” is an art-recognized term, and includesmolecules that facilitate the intracellular delivery of a therapeuticagent or other material. Examples of delivery agents include: sterols(e.g., cholesterol) and lipids (e.g., a cationic lipid, virosome orliposome).

The term “lipid” is art-recognized and is used herein to refer to a fatsoluble naturally occurring molecule. “Lipid” is also used herein torefer to a molecule with a charged portion and a hydrophobic hydrocarbonchain. Herein, the term “lipid” includes the molecules comprisingliposomes.

The term “metal” is art-recognized and is used herein to refer togenerally to elements in Groups 1-13/Groups I-IIIA and I-VIIIB(including transition metals, lanthanides, actinides, alkali metals, andalkaline earth metals), as well as silicon, germanium, tin, lead,antimony, bismuth, and polonium. Herein, iron, copper, silver, platinum,vanadium, ruthenium, manganese, barium, boron, lanthanides, rhenium,technetium, silicon, and others are considered metals. The term “metaloxides” as used herein refers to oxides of such metals, including silica(silicon dioxide), alumina (aluminum oxide), barium oxide, etc.

The term “microspheres” is art-recognized, and includes substantiallyspherical colloidal structures, e.g., formed from biocompatible polymerssuch as subject compositions, having a size ranging from about one orgreater up to about 1000 microns. In general, “microcapsules,” also anart-recognized term, may be distinguished from microspheres, becausemicrocapsules are generally covered by a substance of some type, such asa polymeric formulation. The term “microparticles” is alsoart-recognized, and includes microspheres and microcapsules, as well asstructures that may not be readily placed into either of the above twocategories, all with dimensions on average of less than about 1000microns. A microparticle may be spherical or nonspherical and may haveany regular or irregular shape. If the structures are less than aboutone micron in diameter, then the corresponding art-recognized terms“nanosphere,” “nanocapsule,” and “nanoparticle” may be utilized. Incertain embodiments, the nanospheres, nanocapsules and nanoparticleshave an average diameter of about 500 nm, 200 nm, 100, 50 nm, 10 nm, or1 nm.

A composition comprising microparticles or nanoparticles may includeparticles of a range of particle sizes. In certain embodiments, theparticle size distribution may be uniform, e.g., within less than abouta 20% standard deviation of the median volume diameter, and in otherembodiments, still more uniform, e.g., within about 10% of the medianvolume diameter.

The term “mucolytic agent” is art-recognized, and includes substancesthat are used clinically to increase the rate of mucus clearance (Hanes,J., M. Dawson, Y. Har-el, J. Suh, and J. Fiegel, Gene Delivery to theLung. Pharmaceutical Inhalation Aerosol Technology, A. J. Hickey,Editor. Marcel Dekker Inc.: New York, 2003: p. 489-539, incorporatedherein by reference). Such substances include, for example, N-AcetyleCysteine (NAC), which cleaves disulphide and sulfhydryl bonds present inmucin. Additional examples of mucolytics include mugwort, bromelain,papain, clerodendrum, acetylcysteine, bromhexine, carbocisteine,eprazinone, mesna, ambroxol, sobrerol, domiodol, letosteine, stepronin,tiopronin, gelsolin, thymosin β4, dornase alfa, neltenexine, erdosteine,and various DNases including rhDNase.

The term “mucus” is art-recognized and is used herein to refer to anatural substance that is viscous and comprises mucin glycoproteins.Mucus may be found in a human or a nonhuman animal, such as primates,mammals, and vertebrates. Mucus may be found in a healthy or diseasedhuman or nonhuman animal. Mucus may be cervicovaginal, pulmonary,gastrointestinal, nasal, respiratory, or rectal. The term “mucus” asused herein refers to fresh, undiluted mucus unless otherwise specified.

The term “mucus-resistant” is used herein to refer to the property ofhaving reduced or low mucoadhesion, or to the property of having high orincreased rate of diffusion through mucus. “Mucus-resistant” may be usedherein to refer to a particle that diffuses through human cervicovaginalmucus at a rate that is greater than 1/1000, 1/500, 1/20, 1/10, 1/5, or1/2 the rate that the particle diffuses through water. “Mucus-resistant”may additionally be used herein to refer to a particle that moves inmucus at a rate more than 1×10⁻³, 2×10⁻³, 5×10⁻³, 1×10⁻², 2×10⁻²,2×10⁻², 4×10⁻², 1×10⁻¹, 2×10⁻¹, 5×10⁻¹, 1, or 2 μm²/s at a time scale of1 s. “Mucus-resistant” may additionally be used herein to refer to aparticle that diffuses through a mucosal barrier at a greater rate thana corresponding non-mucus-resistant particle, e.g. a carboxyl-modifiedpolystyrene particle of similar size and density wherein the carboxylmodifications are present at a density of 1.77 to 6.69 carboxyls pernm², wherein the mucus-resistant particle passes through a mucosalbarrier at a rate that is at least 10, 20, 30, 50, 100, 200, 500, 1000,2000, 5000, 10000—or greater fold higher than said correspondingnon-mucus-resistant particle, e.g. a carboxyl-modified polystyreneparticle of similar size and density wherein the carboxyl modificationsare present at a density of 1.77 to 6.69 carboxyls per nm². Saidcorresponding non-mucus-resistant particle may also be an amine-modifiedpolystyrene particle or a sulfate-aldehyde-modified polystyreneparticle.

The term “nucleic acid” is used herein to refer to DNA or RNA includingplasmids, gene therapy vectors, siRNA expression constructs, and siRNAs.

The term “nucleic acid analog” is used herein to refer to non-naturalvariants of nucleic acids including morpholinos, 2′O-modified nucleicacids, and peptide nucleic acids (PNAs)

The term “particle” is art-recognized, and includes, for example,polymeric particles, liposomes, metals, and quantum dots. A particle maybe spherical or nonspherical. A particle may be used, for example, fordiagnosing a disease or condition, treating a disease or condition, orpreventing a disease or condition.

The phrases “parenteral administration” and “administered parenterally”are art-recognized terms, and include modes of administration other thanenteral and topical administration, such as injections, and includewithout limitation intravenous, intramuscular, intrapleural,intravascular, intrapericardial, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradennal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intra-articular, subcapsular,subarachnoid, intraspinal and intrasternal injection and infusion.

The term “peptidomimetic” is art-recognized and refers to a smallprotein-like chain designed to mimic a peptide. A peptidomimetic mayincorporate modifications such as altered backbones and theincorporation of nonnatural amino acids.

The term “peptide” is art-recognized and refers to a polymer of aminoacids. A peptide may be a protein, polypeptide, and/or oligopeptide.

The term “RNA” is art-recognized and refers herein to a ribonucleicacid. RNA may include, for example, mRNA, the transcript of an RNAiconstruct, or an siRNA.

The term “sacrificial agent” is used herein to refer to an agent thatpromotes transport of active particles through mucus, e.g., increase therate at which the active particles move through the mucus, withoutdegrading the mucus (e.g., is not a mucolytic agent). Without wishing tobe bound by theory, it is believed that such sacrificial particlesinteract with the mucus and alter either the structural or adhesiveproperties of mucus such that the active particles experience decreasedmucoadhesion. A sacrificial agent may be a particle (e.g., amicroparticle or a nanoparticle) or a polymer (including, for example,PEG).

“SiRNA” is used herein to refer to an exogenous double-stranded RNA ofapproximately 20-25 nucleotides that decreases expression of one or moregenes by base-pairing with the mRNA of said gene(s) and causingdegradation of the target mRNA.

The term “surfactant” is art-recognized and herein refers to an agentthat lowers the surface tension of a liquid.

The term “therapeutic agent” is art-recognized and may comprise anucleic acid, a nucleic acid analog, a small molecule, a peptidomimetic,a protein, peptide, lipid, or surfactant, and a combination thereof.

The term “treating” is art-recognized and includes preventing a disease,disorder or condition from occurring in an animal which may bepredisposed to the disease, disorder and/or condition but has not yetbeen diagnosed as having it; inhibiting the disease, disorder orcondition, e.g., impeding its progress; and relieving the disease,disorder, or condition, e.g., causing regression of the disease,disorder and/or condition. Treating the disease or condition includesameliorating at least one symptom of the particular disease orcondition, even if the underlying pathophysiology is not affected, suchas treating the pain of a subject by administration of an analgesicagent even though such agent does not treat the cause of the pain.

The term “targeting moiety” is art-recognized and is used herein torefer to a moiety that localizes to or away from a specific locale. Saidmoiety may be, for example, a protein, nucleic acid, nucleic acidanalog, carbohydrate, or small molecule. Said entity may be, forexample, a therapeutic compound such as a small molecule, or adiagnostic entity such as a detectable label. Said locale may be atissue, a particular cell type, or a subcellular compartment. In oneembodiment, the targeting moiety directs the localization of an activeentity. Said active entity may be a small molecule, protein, polymer, ormetal. Said active entity may be useful for therapeutic or diagnosticpurposes.

Viscosity is understood herein as it is recognized in the art to be theinternal friction of a fluid or the resistance to flow exhibited by afluid material when subjected to deformation. The degree of viscosity ofthe polymer can be adjusted by the molecular weight of the polymer, aswell as by varying the proportion of its various monomer subunits; othermethods for altering the physical characteristics of a specific polymerwill be evident to practitioners of ordinary skill with no more thanroutine experimentation. The molecular weight of the polymer used in thecomposition of the invention can vary widely, depending on whether arigid solid state (higher molecular weights) is desirable, or whether afluid state (lower molecular weights) is desired.

The phrase “pharmaceutically acceptable” is art-recognized. In certainembodiments, the term includes compositions, polymers and othermaterials and/or dosage forms which are, within the scope of soundmedical judgment, suitable for use in contact with the tissues of humanbeings and animals without excessive toxicity, irritation, allergicresponse, or other problem or complication, commensurate with areasonable benefit/risk ratio.

The phrase “pharmaceutically acceptable carrier” is art-recognized, andincludes, for example, pharmaceutically acceptable materials,compositions or vehicles, such as a liquid or solid filler, diluent,solvent or encapsulating material involved in carrying or transportingany subject composition, from one organ, or portion of the body, toanother organ, or portion of the body. Each carrier must be “acceptable”in the sense of being compatible with the other ingredients of a subjectcomposition and not injurious to the patient. In certain embodiments, apharmaceutically acceptable carrier is non-pyrogenic. Some examples ofmaterials which may serve as pharmaceutically acceptable carriersinclude: (1) sugars, such as lactose, glucose and sucrose; (2) starches,such as corn starch and potato starch; (3) cellulose, and itsderivatives, such as sodium carboxymethyl cellulose, ethyl cellulose andcellulose acetate; (4) powdered tragacanth; (5) malt; (6) gelatin; (7)talc; (8) cocoa butter and suppository waxes; (9) oils, such as peanutoil, cottonseed oil, sunflower oil, sesame oil, olive oil, corn oil andsoybean oil; (10) glycols, such as propylene glycol; (11) polyols, suchas glycerin, sorbitol, mannitol and polyethylene glycol; (12) esters,such as ethyl oleate and ethyl laurate; (13) agar; (14) bufferingagents, such as magnesium hydroxide and aluminum hydroxide; (15) alginicacid; (16) pyrogen-free water; (17) isotonic saline; (18) Ringer'ssolution; (19) ethyl alcohol; (20) phosphate buffer solutions; and (21)other non-toxic compatible substances employed in pharmaceuticalformulations.

The term “pharmaceutically acceptable salts” is art-recognized, andincludes relatively non-toxic, inorganic and organic acid addition saltsof compositions, including without limitation, analgesic agents,therapeutic agents, other materials and the like. Examples ofpharmaceutically acceptable salts include those derived from mineralacids, such as hydrochloric acid and sulfuric acid, and those derivedfrom organic acids, such as ethanesulfonic acid, benzenesulfonic acid,p-toluenesulfonic acid, and the like. Examples of suitable inorganicbases for the formation of salts include the hydroxides, carbonates, andbicarbonates of ammonia, sodium, lithium, potassium, calcium, magnesium,aluminum, zinc and the like. Salts may also be formed with suitableorganic bases, including those that are non-toxic and strong enough toform such salts. For purposes of illustration, the class of such organicbases may include mono-, di-, and trialkylamines, such as methylamine,dimethylamine, and triethylamine; mono-, di- or trihydroxyalkylaminessuch as mono-, di-, and triethanolamine; amino acids, such as arginineand lysine; guanidine; N-methylglucosamine; N-methylglucamine;L-glutamine; N-methylpiperazine; morpholine; ethylenediamine;N-benzylphenethylamine; (trihydroxymethyl)aminoethane; and the like.See, for example, J. Pharm. Sci. 66: 1-19 (1977), incorporated herein byreference.

A “patient,” “subject,” or “host” to be treated by the subject methodmay mean either a human or non-human animal, such as primates, mammals,and vertebrates.

The term “prophylactic or therapeutic” treatment is art-recognized andincludes administration to the host of one or more of the subjectcompositions. If it is administered prior to clinical manifestation ofthe unwanted condition (e.g., disease or other unwanted state of thehost animal) then the treatment is prophylactic, i.e., it protects thehost against developing the unwanted condition, whereas if it isadministered after manifestation of the unwanted condition, thetreatment is therapeutic, (i.e., it is intended to diminish, ameliorate,or stabilize the existing unwanted condition or side effects thereof).

The term “preventing” is art-recognized, and when used in relation to acondition, such as a local recurrence (e.g., pain), a disease such ascancer, a syndrome complex such as heart failure or any other medicalcondition, is well understood in the art, and includes administration ofa composition which reduces the frequency of, or delays the onset of,symptoms of a medical condition in a subject relative to a subject whichdoes not receive the composition. Thus, prevention of cancer includes,for example, reducing the number of detectable cancerous growths in apopulation of patients receiving a prophylactic treatment relative to anuntreated control population, and/or delaying the appearance ofdetectable cancerous growths in a treated population versus an untreatedcontrol population, e.g., by a statistically and/or clinicallysignificant amount. Prevention of an infection includes, for example,reducing the number of diagnoses of the infection in a treatedpopulation versus an untreated control population, and/or delaying theonset of symptoms of the infection in a treated population versus anuntreated control population. Prevention of pain includes, for example,reducing the magnitude of, or alternatively delaying, pain sensationsexperienced by subjects in a treated population versus an untreatedcontrol population.

The phrase “prolonged residence time” is art-recognized and refers to anincrease in the time required for an agent to be cleared from apatient's body, or organ or tissue of that patient. In certainembodiments, “prolonged residence time” refers to an agent that iscleared with a half-life that is 10%, 20%, 50% or 75% longer than astandard of comparison such as a comparable agent without amucus-resistant coating. In certain embodiments, “prolonged residencetime” refers to an agent that is cleared with a half-life of 2, 5, 10,20, 50, 100, 200, 500, 1000, 2000, 5000, or 10000 times longer than astandard of comparison such as a comparable agent without amucus-resistant coating.

The term “protein” is art-recognized and is used herein to refer to apolymer of amino acids.

The phrases “systemic administration,” “administered systemically,”“peripheral administration” and “administered peripherally” areart-recognized, and include the administration of a subject composition,therapeutic or other material at a site remote from the disease beingtreated. Administration of an agent directly into, onto, or in thevicinity of a lesion of the disease being treated, even if the agent issubsequently distributed systemically, may be termed “local” or“topical” or “regional” administration, other than directly into thecentral nervous system, e.g., by subcutaneous administration, such thatit enters the patient's system and, thus, is subject to metabolism andother like processes.

The phrase “therapeutically effective amount” is an art-recognized term.In certain embodiments, the term refers to an amount of the therapeuticagent that, when incorporated into a polymer of the present invention,produces some desired effect at a reasonable benefit/risk ratioapplicable to any medical treatment. In certain embodiments, the termrefers to that amount necessary or sufficient to eliminate or reducesensations of pain for a period of time. The effective amount may varydepending on such factors as the disease or condition being treated, theparticular targeted constructs being administered, the size of thesubject, or the severity of the disease or condition. One of ordinaryskill in the art may empirically determine the effective amount of aparticular compound without necessitating undue experimentation.

The term “ED₅₀” is art-recognized. In certain embodiments, ED₅₀ meansthe dose of a drug that produces 50% of its maximum response or effect,or, alternatively, the dose that produces a pre-determined response in50% of test subjects or preparations.

The term “LD₅₀” is art-recognized. In certain embodiments, LD₅₀ meansthe dose of a drug that is lethal in 50% of test subjects. The term“therapeutic index” is an art-recognized term that refers to thetherapeutic index of a drug, defined as LD₅₀/ED₅₀.

The terms “incorporated” and “encapsulated” are art-recognized when usedin reference to a therapeutic agent, or other material and a polymericcomposition, such as a composition of the present invention. In certainembodiments, these terms include incorporating, formulating, orotherwise including such agent into a composition that allows forrelease, such as sustained release, of such agent in the desiredapplication. The terms contemplate any manner by which a therapeuticagent or other material is incorporated into a polymer matrix, includingfor example: attached to a monomer of such polymer (by covalent, ionic,or other binding interaction), physical admixture, enveloping the agentin a coating layer of polymer, and having such monomer be part of thepolymerization to give a polymeric formulation, distributed throughoutthe polymeric matrix, appended to the surface of the polymeric matrix(by covalent or other binding interactions), encapsulated inside thepolymeric matrix, etc. The term “co-incorporation” or “co-encapsulation”refers to-the incorporation of a therapeutic agent or other material andat least one other therapeutic agent or other material in a subjectcomposition.

More specifically, the physical form in which any therapeutic agent orother material is encapsulated in polymers may vary with the particularembodiment. For example, a therapeutic agent or other material may befirst encapsulated in a microsphere and then combined with the polymerin such a way that at least a portion of the microsphere structure ismaintained. Alternatively, a therapeutic agent or other material may besufficiently immiscible in the polymer of the invention that it isdispersed as small droplets, rather than being dissolved, in thepolymer. Any form of encapsulation or incorporation is contemplated bythe present invention, in so much as the release, preferably sustainedrelease, of any encapsulated therapeutic agent or other materialdetermines whether the form of encapsulation is sufficiently acceptablefor any particular use.

The term “biocompatible plasticizer” is art-recognized, and includesmaterials which are soluble or dispersible in the compositions of thepresent invention, which increase the flexibility of the polymer matrix,and which, in the amounts employed, are biocompatible. Suitableplasticizers are well known in the art and include those disclosed inU.S. Pat. Nos. 2,784,127 and 4,444,933. Specific plasticizers include,by way of example, acetyl tri-n-butyl citrate (c. 20 weight percent orless), acetyltrihexyl citrate (c. 20 weight percent or less), butylbenzyl phthalate, dibutylphthalate, dioctylphthalate, n-butyryltri-n-hexyl citrate, diethylene glycol dibenzoate (c. 20 weight percentor less) and the like.

3. Particles and Related Compositions

The present invention provides particles, such as microparticles ornanoparticles. In certain embodiments, a polymeric particle comprises apharmaceutically acceptable polymer, a bioactive agent, and asurface-altering agent that makes the surface of the polymeric particlemucus resistant. In alternative embodiments, a polymeric particlecomprises a pharmaceutically acceptable polymer and a surface-alteringagent that is also a bioactive agent. In certain such embodiments, theparticle further comprises an adhesion-promoting agent, such asdimethyldioctadecyl-ammonium bromide or other cation-bearing additives,that promotes adhesion of the surface-altering agent to the surface ofthe particle. The surface-altering agent may increase particle transportrates in mucus.

Examples of the surface-altering agents include but are not limited toanionic protein (e.g., bovine serum albumin), surfactants (e.g.,cationic surfactants such as for example dimethyldioctadecyl-ammoniumbromide), sugars or sugar derivatives (e.g., cyclodextrin), nucleicacids, and polymers (e.g., heparin, polyethylene glycol and poloxomer).Surface-altering agents may also include mucolytic agents, e.g.,N-acetylcysteine, mugwort, bromelain, papain, clerodendrum,acetyleysteine, bromhexine, carbocisteine, eprazinone, mesna, ambroxol,sobrerol, domiodol, letosteine, stepronin, tiopronin, gelsolin, thymosinβ4 dornase alfa, neltenexine, erdosteine, and various DNases includingrhDNase. A mucolytic agent or sacrificial agent can be administeredseparately or concomitantly with a particle, or as a surface-alteringagent of the particle (e.g., coated upon, covalently coupled to,co-localized with, or encapsulated within the particle) of the inventionto improve transport across a mucosal barrier. Certain agents, e.g.,cyclodextrin, may form inclusion complexes with other molecules and canbe used to form attachments to additional moieties and facilitate thefunctionalization of the particle surface and/or the attached moleculesor moieties.

Examples of suitable surface-altering agents that are carbohydratesinclude agar, agarose, alginic acid, amylopectin, amylose, beta-glucan,callose, carrageenan, cellodextrins, cellulin, cellulose, chitin,chitosan, chrysolaminarin, curdlan, cyclodextrin, dextrin, ficoll,fructan, fucoidan, galactomannan, gellan gum, glucan, glucomannan,glycocalyx, glycogen, hemicellulose, hydroxyethyl starch, kefiran,laminarin, mucilage, glycosaminoglycan, natural gum, paramylon, pectin,polysaccharide peptide, schizophyllan, sialyl lewis x, starch, starchgelatinization, sugammadex, xanthan gum, and xyloglucan, as well asfragments and derivatives of such carbohydrates.

Examples of surfactants include but are not limited toL-at-phosphatidylcholine (PC), 1,2-dipalmitoylphosphatidycholine (DPPC),oleic acid, sorbitan trioleate, sorbitan mono-oleate, sorbitanmonolaurate, polyoxyethylene (20) sorbitan monolaurate, polyoxyethylene(20) sorbitan monooleate, natural lecithin, oleyl polyoxyethylene (2)ether, stearyl polyoxyethylene (2) ether, lauryl polyoxyethylene (4)ether, block copolymers of oxyethylene and oxypropylene, syntheticlecithin, diethylene glycol dioleate, tetrahydrofurfuryl oleate, ethyloleate, isopropyl myristate, glyceryl monooleate, glyceryl monostearate,glyceryl monoricinoleate, cetyl alcohol, stearyl alcohol, polyethyleneglycol 400, cetyl pyridinium chloride, benzalkonium chloride, olive oil,glyceryl monolaurate, corn oil, cotton seed oil, and sunflower seed oil,lecithin, oleic acid, and sorbitan trioleate.

A pharmaceutically acceptable polymer may be a poly(lactic-co-glycolic)acid (PLGA), poly(D,L-lactic-co-glycolic) acid), polyethylenimine,dioleyltrimethyammoniumpropane/dioleyl-sn-glycerolphosphoethanolamine,polysebacic anhydrides, or other polymers formed from clinicallyapproved monomers. Examples of clinically approved monomers include butare not limited to monomers of sebacic acid and1,3-bis(carboxyphenoxy)propane.

A pharmaceutically acceptable polymer may be a polyanhydride polymercomprising repeated subunits of Formula A and Formula B, and,optionally, subunits of Formula C, as depicted below:

wherein, as valence and stability permit,

-   M represents, independently for each occurrence, a substituted or    unsubstituted methylene, e.g., CH₂, CH(Me), CF₂, CH(OH), C═O, etc.,    preferably CH₂ or, for an occurrence of M adjacent to O, C═O;-   X is absent or, independently for each occurrence, represents a    heteroatom selected from NR, O, and S, preferably O;-   R represents, independently for each occurrence, H or lower alkyl;-   j represents, independently for each occurrence, an integer from 0    to 16, preferably from 1 to 9;-   m represents, independently for each occurrence, an integer from 4    to 20, preferably from 8 to 14, even more preferably 10;-   n represents, independently for each occurrence, an integer from 4    to 500, preferably from 10 to 200;-   p represents, independently for each occurrence, an integer from 1    to 60, preferably from 4 to 40; and-   q represents, independently for each occurrence, an integer from 1    to 20, preferably from 2 to 10, even more preferably from 2 to 6.

In certain embodiments, m, n, and q each, independently, represent aconstant value throughout the polymer, i.e., m, n, and q do not varywithin a subunit of Formula A, B, or C, or within different subunits ofthe same formula, within a sample of polymer or a polymer chain.

In certain embodiments, the polymer may contain monomeric units otherthan those subunits represented by Formulae A, B, and C. In preferredembodiments, however, the polymer consists essentially of subunits ofFormulae A, B, and C.

In certain embodiments, a polymer of the present invention has theformula -[K]_(n)-, wherein each occurrence of K represents a subunit ofFormula A or B or, optionally. C, as set forth above. Polymer strandsmay be capped (terminated) with hydroxyl groups (to form carboxylicacids), acyl groups (to form anyhydrides), alkoxy groups (to formesters), or any other suitable capping groups.

In certain embodiments, the subunits of Formula B have a molecularweight between 200 and 1000 daltons, while in other embodiments, thesubunits of Formula B have a molecular weight between 4000 and 10,000daltons. In some embodiments, the subunits of Formula B have molecularweights which vary throughout the polymer between 200 daltons and 10,000or more daltons, while in other embodiments, the subunits of Formula Bhave molecular weights that vary only within a narrow range (e.g.,200-300 daltons, or 2,000-3,000 daltons).

In certain embodiments, subunits of Formula B make up between 1 and 80%of the polymer, by weight, preferably between 5 and 60%. In certainembodiments, subunits of Formula C, if present, may make up between 1%and 80% of the polymer, by weight, preferably between 5 and 60%. Incertain embodiments, subunits of Formula A make up between 10% and 99%of the polymer, by weight, preferably between 15% and 95%.

Each subunit may repeat any number of times, and one subunit may occurwith substantially the same frequency, more often, or less often thananother subunit, such that both subunits may be present in approximatelythe same amount, or in differing amounts, which may differ slightly orbe highly disparate, e.g., one subunit is present nearly to theexclusion of the other.

In certain instances, the polymers are random copolymers, in which thedifferent subunits and/or other monomeric units are distributed randomlythroughout the polymer chain. In part, the term “random” is intended torefer to the situation in which the particular distribution orincorporation of monomeric units in a polymer that has more than onetype of monomeric unit is not directed or controlled directly by thesynthetic protocol, but instead results from features inherent to thepolymer system, such as the reactivity, amounts of subunits and othercharacteristics of the synthetic reaction or other methods ofmanufacture, processing or treatment.

In certain embodiments, the polymeric chains of such compositions, e.g.,which include repetitive elements shown in any of the above formulas,have molecular weights (M_(w)) ranging from about 2000 or less to about300,000, 600,000 or 1,000,000 or more daltons, or alternatively at leastabout 10,000, 20,000, 30,000, 40,000, or 50,000 daltons, moreparticularly at least about 100,000 daltons. Number-average molecularweight (M_(n)) may also vary widely, but generally falls in the range ofabout 1,000 to about 200,000 daltons, preferably from about 10,000 toabout 100,000 daltons and, even more preferably, from about 8,000 toabout 50,000 daltons. Most preferably, M_(n) varies between about 12,000and 45,000 daltons. Within a given sample of a polymer, a wide range ofmolecular weights may be present. For example, molecules within thesample may have molecular weights that differ by a factor of 2, 5, 10,20, 50, 100, or more, or that differ from the average molecular weightby a factor of 2, 5, 10, 20, 50, 100, or more.

One method to determine molecular weight is by gel permeationchromatography (“GPC”), e.g., mixed bed columns, CH₂Cl₂ solvent, lightscattering detector, and off-line dn/dc. Other methods are known in theart.

Other polymers that may be employed to make the polymeric particles ofthe invention include but are not limited to cyclodextrin-containingpolymers, in particular cationic cyclodextrin-containing polymers, suchas those described in U.S. Pat. No. 6,509,323, poly(caprolactone) (PCL),ethylene vinyl acetate polymer (EVA), poly(lactic acid) (PLA),poly(L-lactic acid) (PLLA), poly(glycolic acid) (PGA), poly(lacticacid-co-glycolic acid) (PLGA), poly(L-lactic acid-co-glycolic acid)(PLLGA), poly(D,L-lactide) (PDLA), poly(L-lactide) (PLLA),poly(D,L-lactide-co-caprolactone),poly(D,L-lactide-co-caprolactone-co-glycolide),poly(D,L-lactide-co-PEO-co-D,L-lactide),poly(D,L-lactide-co-PPO-co-D,L-lactide), polyalkyl cyanoacralate,polyurethane, poly-L-lysine (PLL), hydroxypropyl methacrylate (HPMA),polyethyleneglycol, poly-L-glutamic acid, poly(hydroxy acids),polyanhydrides, polyorthoesters, poly(ester amides), polyamides,poly(ester ethers), polycarbonates, polyalkylenes such as polyethyleneand polypropylene, polyalkylene glycols such as poly(ethylene glycol)(PEG), polyalkylene oxides (PEO), polyalkylene terephthalates such aspoly(ethylene terephthalate), polyvinyl alcohols (PVA), polyvinylethers, polyvinyl esters such as poly(vinyl acetate), polyvinyl halidessuch as poly(vinyl chloride) (PVC), polyvinylpyrrolidone, polysiloxanes,polystyrene (PS), polyurethanes, derivatized celluloses such as alkylcelluloses, hydroxyalkyl celluloses, cellulose ethers, cellulose esters,nitro celluloses, hydroxypropylcellulose, carboxymethylcellulose,polymers of acrylic acids, such as poly(methyl(meth)acrylate) (PMMA),poly(ethyl(meth)acrylate), poly(butyl(meth)acrylate),poly(isobutyl(meth)acrylate), poly(hexyl(meth)acrylate),poly(isodecyl(meth)acrylate), poly(lauryl(meth)acrylate),poly(phenyl(meth)acrylate), poly(methyl acrylate), poly(isopropylacrylate), poly(isobutyl acrylate), poly(octadecyl acrylate) (jointlyreferred to herein as “polyacrylic acids”), and copolymers and mixturesthereof, polydioxanone and its copolymers, polyhydroxyalkanoates,poly(propylene fumarate), polyoxymethylene, poloxamers,poly(ortho)esters, poly(butyric acid), poly(valeric acid),poly(lactide-co-caprolactone), trimethylene carbonate,polyvinylpyrrolidone, and the polymers described in Shieh et al., 1994,J. Biomed. Mater. Res., 28, 1465-1475, and in U.S. Pat. No. 4,757,128,Hubbell et al., U.S. Pat. Nos. 5,654,381; 5,627,233; 5,628,863;5,567,440; and 5,567,435, all of which are incorporated herein byreference. Other suitable polymers include polyorthoesters (e.g. asdisclosed in Heller et al., 2000, Eur. J. Pharm. Biopharm., 50:121-128),polyphosphazenes (e.g. as disclosed in Vandorpe et al., 1997,Biomaterials, 18:1147-1152), and polyphosphoesters (e.g. as disclosed inEncyclopedia of Controlled Drug Delivery, pp. 45-60, Ed. E. Mathiowitz,John Wiley & Sons, Inc. New York, 1999), all of which are incorporatedherein by reference, as well as blends and/or block copolymers of two ormore such polymers. The carboxyl termini of lactide- andglycolide-containing polymers may optionally be capped, e.g., byesterification, and the hydroxyl termini may optionally be capped, e.g.by etherification or esterification.

Copolymers of two or more polymers described above, including blockand/or random copolymers, may also be employed to make the polymericparticles of the invention.

The invention also contemplates employing copolymers of PEG orderivatives thereof (such as units of Formula B, above) with any of thepolymers described above to make the polymeric particles of theinvention. In certain embodiments, the PEG or derivatives may locate inthe interior positions of the copolymer. Alternatively, the PEG orderivatives may locate near or at the terminal positions of thecopolymer. In certain embodiments, the microparticles or nanoparticlesare formed under conditions that allow regions of PEG to phase separateor otherwise locate to the surface of the particles. While in certainembodiments, the surface-localized PEG regions alone may perform thefunction of a surface-altering agent, in other embodiments thesecopolymeric particles comprise an additional surface-altering agent.Such techniques may be applied analogously to form copolymers of othersuitable surface-altering agent polymers, such ascyclodextrin-containing polymers, polyanionic polymers, etc.

In certain embodiments, the polymers are soluble in one or more commonorganic solvents for ease of fabrication and processing. Common organicsolvents include such solvents as 2,2,2-trifluoroethanol, chloroform,dichloromethane, dichloroethane, 2-butanone, butyl acetate, ethylbutyrate, acetone, ethyl acetate, dimethylacetamide, N-methylpyrrolidone, dimethylformamide, and dimethylsulfoxide.

In certain embodiments, the subject particles and compositions include abioactive agent. A bioactive agent may be a therapeutic agent, adiagnostic agent, or an imaging agent. Examples of therapeutic agentsinclude but are not limited to a nucleic acid or nucleic acid analog(e.g., a DNA or an RNA), a small molecule, a peptidomimetic, a protein,or a combination thereof. In certain embodiments, the diagnostic orimaging agent further comprises a detectable label.

A bioactive agent may be a nucleic acid or analog thereof, e.g., a DNAuseful in gene therapy. Alternatively or additionally, an RNA may beemployed as a bioactive agent. The RNA may be an RNAi molecule orconstruct. RNAi refers to “RNA interference,” by which expression of agene or gene product is decreased by introducing into a target cell oneor more double-stranded RNAs which are homologous to the gene ofinterest (particularly to the messenger RNA of the gene of interest).RNAi may also be achieved by introduction of a DNA:RNA complex whereinthe antisense strand (relative to the target) is RNA. Either strand mayinclude one or more modifications to the base or sugar-phosphatebackbone. Any nucleic acid preparation designed to achieve an RNAinterference effect is referred to herein as an siRNA construct.

Alternatively, an antisense nucleic acid is employed as a bioactiveagent. An antisense nucleic acid may bind to its target by conventionalbase pair complementarity, or, for example, in the case of binding toDNA duplexes, through specific interactions in the major groove of thedouble helix. The antisense oligonucleotides can be DNA or RNA orchimeric mixtures or derivatives or modified versions thereof,single-stranded or double-stranded. The oligonucleotide can be modifiedat the base moiety, sugar moiety, or phosphate backbone, for example, toimprove stability of the molecule, hybridization, etc. Theoligonucleotide may include other appended groups such as peptides(e.g., for targeting host cell receptors), or agents facilitatingtransport across the cell membrane (see, e.g., Letsinger et al., 1989,Proc. Natl. Acad. Sci. U.S.A. 86:6553-6556, Lemaitre et al., 1987, Proc.Natl. Acad. Sci. 84:648-652, PCT Publication No. WO 88/09810, publishedDec. 15, 1988, all of which are incorporated herein by reference) or theblood-brain barrier (see, e.g., PCT Publication No. WO 89/10134,published Apr. 25, 1988, incorporated herein by reference),hybridization-triggered cleavage agents (see, e.g., Krol et al., 1988,BioTechniques 6:958-976, incorporated herein by reference) orintercalating agents (see, e.g., Zon, 1988, Pharm. Res. 5:539-549,incorporated herein by reference). To this end, the oligonucleotide maybe conjugated to another molecule, e.g., a peptide, hybridizationtriggered cross-linking agent, transport agent, hybridization-triggeredcleavage agent, etc.

“Small molecule” as used herein is meant to refer to a molecule having amolecular weight of less than about 3 kDa and most preferably less thanabout 1.5 kDa. Extensive libraries of chemical and/or biologicalmixtures comprising arrays of small molecules and/or fungal, bacterial,or algal extracts can be screened with any of the assays known in theart to obtain a desirable bioactive agent for use in or with a particleof the invention.

Peptidomimetics are compounds in which at least a portion of a peptide,such as a therapeutic peptide, is modified, and the three-dimensionalstructure of the peptidomimetic remains substantially the same as thatof the peptide. Peptidomimetics (both peptide and non-peptidylanalogues) may have improved properties (e.g., decreased proteolysis,increased retention or increased bioavailability). Peptidomimeticsgenerally have improved oral availability, which makes them especiallysuited to treatment of disorders in a human or animal. It should benoted that peptidomimetics may or may not have similar two-dimensionalchemical structures, but share common three-dimensional structuralfeatures and geometry.

The term “protein,” “polypeptide,” and “peptide” are usedinterchangeably herein and generally refer to a polymer formed by atleast two amino acids linked via a peptide bond.

Imaging agents (e.g., detectable labels or bioactive agents linked to adetectable label), therapeutic agents, and targeting moieties, such asthose described in U.S. Patent Application Publication No. 20030049203,incorporated herein by reference, are also contemplated and can beemployed with the particles of the present invention.

In certain embodiments, a particle of the invention comprises an imagingagent that may be further attached to a detectable label (e.g., thelabel can be a radioisotope, fluorescent compound, enzyme or enzymeco-factor). The active moiety may be a radioactive agent, such as:radioactive heavy metals such as iron chelates, radioactive chelates ofgadolinium or manganese, positron emitters of oxygen, nitrogen, iron,carbon, or gallium, a ⁴³K, ⁵²Fe, ⁵⁷Co, ⁶⁷Cu, ⁶⁷Ga, ⁶⁸Ga, ¹²³I, ¹²⁵I,¹³¹I, ¹³²I, or ⁹⁹Tc. A particle including such a moiety may be used asan imaging agent and be administered in an amount effective fordiagnostic use in a mammal such as a human. In this manner, thelocalization and accumulation of the imaging agent can be detected. Thelocalization and accumulation of the imaging agent may be detected byradioscintiography, nuclear magnetic resonance imaging, computedtomography, or positron emission tomography. As will be evident to theskilled artisan, the amount of radioisotope to be administered isdependent upon the radioisotope. Those having ordinary skill in the artcan readily formulate the amount of the imaging agent to be administeredbased upon the specific activity and energy of a given radionuclide usedas the active moiety. Typically 0.1-100 millicuries per dose of imagingagent, preferably 1-10 millicuries, most often 2-5 millicuries areadministered. Thus, compositions according to the present inventionuseful as imaging agents comprising a targeting moiety conjugated to aradioactive moiety comprise 0.1-100 millicuries, in some embodimentspreferably 1-10 millicuries, in some embodiments preferably 2-5millicuries, in some embodiments more preferably 1-5 millicuries.

The means of detection used to detect the label is dependent of thenature of the label used and the nature of the biological sample used,and may also include fluorescence polarization, high performance liquidchromatography, antibody capture, gel electrophoresis, differentialprecipitation, organic extraction, size exclusion chromatography,fluorescence microscopy, or fluorescence activated cell sorting (FACS)assay.

In certain embodiments, a bioactive agent or targeting moiety may becovalently coupled to a particle of the invention. In such embodiments,the bioactive agent may preferably be a hydrophilic or charged agent,such that its presence on the surface of the particle increases chargeor hydrophilicity of the particle or otherwise increases the particle'smucus resistance.

The covalent linkage may be selected to be cleaved under biologicalconditions, e.g., by chemical or enzymatic hydrolysis or other cleavageprocesses.

In certain embodiments, a particle of the invention may further comprisea targeting moiety or molecule. The targeting molecule may be covalentlylinked to any other component of the particle, such as the polymer or asurface-altering agent. The targeting molecule may also be co-localizedwith a particle, using methods known in the art. The targeting moleculemay direct the particle, and thus the included bioactive agent, to adesirable target or location in a patient.

In one embodiment, the targeting moiety is a small molecule. Moleculeswhich may be suitable for use as targeting moieties in the presentinvention include haptens, epitopes, and dsDNA fragments and analogs andderivatives thereof. Such moieties bind specifically to antibodies,fragments or analogs thereof, including mimetics (for haptens andepitopes), and zinc finger proteins (for dsDNA fragments). Nutrientsbelieved to trigger receptor-mediated endocytosis and therefore usefultargeting moieties include biotin, folate, riboflavin, carnitine,inositol, lipoic acid, niacin, pantothenic acid, thiamin, pyridoxal,ascorbic acid, and the lipid soluble vitamins A, D, E and K. Anotherexemplary type of small molecule targeting moiety includes steroidallipids, such as cholesterol, and steroidal hormones, such as estradiol,testosterone, etc.

In another embodiment, the targeting moiety may comprise a protein.Particular types of proteins may be selected based on knowncharacteristics of the target site or target cells. For example, theprobe can be an antibody either monoclonal or polyclonal, where acorresponding antigen is displayed at the target site. In situationswherein a certain receptor is expressed by the target cells, thetargeting moiety may comprise a protein or peptidomimetic ligand capableof binding to that receptor. Proteins ligands of known cell surfacereceptors include low density lipoproteins, transferrin, insulin,fibrinolytic enzymes, anti-HER2, platelet binding proteins such asannexins, and biological response modifiers (including interleukin,interferon, erythropoietin and colony-stimulating factor). A number ofmonoclonal antibodies that bind to a specific type of cell have beendeveloped, including monoclonal antibodies specific for tumor-associatedantigens in humans. Among the many such monoclonal antibodies that maybe used are anti-TAC, or other interleukin-2 receptor antibodies; 9.2.27and NR-ML-05 to the 250 kilodalton human melanoma-associatedproteoglycan; and NR-LU-10 to a pancarcinoma glycoprotein. An antibodyemployed in the present invention may be an intact (whole) molecule, afragment thereof, or a functional equivalent thereof. Examples ofantibody fragments are F(ab), Fab′, Fab, and F, fragments, which may beproduced by conventional methods or by genetic or protein engineering.

Other preferred targeting moieties include sugars (e.g., glucose,fucose, galactose, mannose) that are recognized by target-specificreceptors. For example, instant claimed constructs can be glycosylatedwith mannose residues (e.g., attached as C-glycosides to a freenitrogen) to yield targeted constructs having higher affinity binding totumors expressing mannose receptors (e.g., glioblastomas andgangliocytomas), and bacteria, which are also known to express mannosereceptors (Bertozzi, C R and M D Bednarski Carbohydrate Research 223:243(1992); 3. Am. Chem. Soc. 114:2242, 5543 (1992)), as well as potentiallyother infectious agents. Certain cells, such as malignant cells andblood cells (e.g., A. AB, B, etc.) display particular carbohydrates, forwhich a corresponding lectin may serve as a targeting moiety.

Covalent linkage may be effected by various methods known in the art.Moieties, such as surface-altering agents, adhesion-promoting agents,bioactive agents, targeting agents, and other functional moietiesdiscussed herein, to be covalently linked to the surface of a particle(pendant moieties) may be coupled to the surface after formation of theparticle, or may be coupled to one or more components prior to formationof the particle, such that, by chance or molecular self-assembly, themoieties locate to the surface of the particle during particleformation, and thus become embedded or enmeshed in the surface of theparticle. In certain embodiments, PEG is covalently linked tonanoparticles by reacting a carboxyl group of the particle with an aminegroup of the PEG, e.g., to form an amide. Moieties may be coupled to thesurface of a formed particle in any order or by any attachment thatmaintains the desired activity of each component, whether in its linkedstate or following cleavage of a biocleavable linkage, for example.Pendant moieties may be affixed to particles or components by linkingfunctional groups present at the termini of those moieties or componentsor by linking appropriate functional groups present at any location oneither component. Alternatively, the various components may be linkedindirectly through a tether molecule as is well known in the art.

Numerous chemical cross-linking methods are known and potentiallyapplicable for conjugating the various portions of the instantconstructs. Many known chemical cross-linking methods are non-specific,i.e., they do not direct the point of coupling to any particular site onthe molecule. As a result, use of non-specific cross-linking agents mayattack functional sites or sterically block active sites, rendering theconjugated molecules inactive.

For coupling simple molecules, it is often possible to control thelocation of coupling by using protecting groups, functionalgroup-selective reactions, or the differential steric accessibility ofparticular sites on the molecules. Such strategies are well known tothose skilled in the art of chemical synthesis. Protecting groups mayinclude but are not limited to N-terminal protecting groups known in theart of peptide syntheses, including t-butoxy carbonyl (BOC), benzoyl(Bz), fluoren-9-ylmethoxycarbonyl (Fmoc), triphenylmethyl(trityl) andtrichloroethoxycarbonxyl (Troc) and the like. The use of variousN-protecting groups, e.g., the benzyloxy carbonyl group or thet-butyloxycarbonyl group (Boc), various coupling reagents, e.g.,dicyclohexylcarbodiimide (DCC), 1,3-diisopropylcarbodiimide (DIC),1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC),N-hydroxyazabenzotriazole (HATU), carbonyldiimidazole, or1-hydroxybenzotriazole monohydrate (HOBT), and various cleavageconditions: for example, trifluoracetic acid (TFA), HCl in dioxane,hydrogenation on Pd—C in organic solvents (such as methanol or ethylacetate), boron tris(trifluoroacetate), and cyanogen bromide, andreaction in solution with isolation and purification of intermediatesare well-known in the art of peptide synthesis, and are equallyapplicable to the preparation of the subject compounds.

A preferred approach to increasing coupling specificity of complexmolecules is direct chemical coupling to a functional group found onlyonce or a few times in one or both of the molecules to be cross-linked.For example, in many proteins, cysteine, which is the only protein aminoacid containing a thiol group, occurs only a few times. Also, forexample, if a peptide contains no lysine residues, a cross-linkingreagent specific for primary amines will be selective for the aminoterminus of that peptide. Successful utilization of this approach toincrease coupling specificity requires that the molecule have thesuitable reactive residues in areas of the molecule that may be alteredwithout loss of the molecule's biological activity.

Coupling of the two constituents can be accomplished via a coupling orconjugating agent. There are several intermolecular cross-linkingreagents which can be utilized. See, e.g., Means, G. E. and Feeney, R.E., Chemical Modification of Proteins, Holden-Day, 1974, pp. 39-43.Among these reagents are, for example, J-succinimidyl3-(2-pyridyldithio) propionate (SPDP) or N,N′-(1,3-phenylene)bismaleimide (both of which are highly specific for sulfhydryl groupsand form irreversible linkages); N,N′-ethylene-bis-(iodoacetamide) orother such reagent having 6 to 11 carbon methylene bridges (whichrelatively specific for sulfhydryl groups); and1,5-difluoro-2,4-dinitrobenzene (which forms irreversible linkages withamino and tyrosine groups). Other cross-linking reagents useful for thispurpose include: p,p′-difluoro-m,m′-dinitrodiphenylsulfone (which formsirreversible cross-linkages with amino and phenolic groups); dimethyladipimidate (which is specific for amino groups);phenol-1,4-disulfonylchloride (which reacts principally with aminogroups); hexamethylenediisocyanate or diisothiocyanate, orazophenyl-p-diisocyanate (which reacts principally with amino groups);glutaraldehyde (which reacts with several different side chains) anddisdiazobenzidine (which reacts primarily with tyrosine and histidine).

Cross-linking reagents may be homobifunctional, i.e., having twofunctional groups that undergo the same reaction. A preferredhomobifunctional cross-linking reagent is bismaleimidohexane (“BMH”).BMH contains two maleimide functional groups, which react specificallywith sulfhydryl-containing compounds under mild conditions (pH 6.5-7.7).The two maleimide groups are connected by a hydrocarbon chain.Therefore, BMH is useful for irreversible cross-linking of peptides thatcontain cysteine residues.

Cross-linking reagents may also be heterobifunctional.Heterobifunctional cross-linking agents have two different functionalgroups, for example an amine-reactive group and a thiol-reactive group,that will cross-link two proteins having free amines and thiols,respectively.

Heterobifunctional cross-linkers provide the ability to design morespecific coupling methods for conjugating two chemical entities, therebyreducing the occurrences of unwanted side reactions such as homo-proteinpolymers. A wide variety of heterobifunctional cross-linkers are knownin the art. Examples of heterobifunctional cross-linking agents aresuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SMCC),N-succinimidyl (4-iodoacetyl) aminobenzoate (SIAB),1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC);4-succinimidyloxycarbonyl-a-methyl-a-(2-pyridyldithio)-tolune (SMPT),N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP), succinimidyl6-[3-(2-pyridyldithio) propionate]hexanoate (LC-SPDP)succinimidyl4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SMCC),m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), and succinimide4-(p-maleimidophenyl)butyrate (SMPB), an extended chain analog of MBS.The succinimidyl group of these cross-linkers reacts with a primaryamine, and the thiol-reactive maleimide forms a covalent bond with thethiol of a cysteine residue.

Cross-linking reagents often have low solubility in water. A hydrophilicmoiety, such as a sulfonate group, may be added to the cross-linkingreagent to improve its water solubility. Sulfo-MBS and sulfo-SMCC areexamples of cross-linking reagents modified for water solubility.

Another reactive group useful as part of a heterobifunctionalcross-linker is a thiol reactive group. Common thiol-reactive groupsinclude maleimides, halogens, and pyridyl disulfides. Maleimides reactspecifically with free sulfhydryls (cysteine residues) in minutes, underslightly acidic to neutral (pH 6.5-7.5) conditions. Haloalkyl groups(e.g., iodoacetyl functions) react with thiol groups at physiologicalpH's. Both of these reactive groups result in the formation of stablethioether bonds.

In addition to the heterobifunctional cross-linkers, there exist anumber of other cross-linking agents including homobifunctional andphotoreactive cross-linkers. Disuccinimidyl —suberate (DSS),bismaleimidohexane (BMH) and dimethylpimelimidate-2 HCl (DMP) areexamples of useful homobifunctional cross-linking agents, andbis-[β-(4-azidosalicylamido)ethyl]disulfide (BASED) andN-succinimidyl-6(4′-azido-2′-nitrophenyl-amino)hexanoate (SANPAH) areexamples of useful photoreactive cross-linkers for use in thisinvention. For a review of protein coupling techniques, see Means et al.(1990) Bioconjugate Chemistry 1:2-12, incorporated by reference herein.

Many cross-linking reagents yield a conjugate that is essentiallynon-cleavable under cellular conditions. However, some cross-linkingreagents contain a covalent bond, such as a disulfide, that is cleavableunder cellular conditions. For example,dithiobis(succinimidylpropionate) (DSP), Traut's reagent andN-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) are well-knowncleavable cross-linkers. The use of a cleavable cross-linking reagentmay permit the moiety, such as a therapeutic agent, to separate from theconstruct after delivery to the target. Direct disulfide linkages mayalso be useful. Additional cleavable linkages are known in the art andmay be employed to advantage in certain embodiments of the presentinvention.

Many methods for linking compounds, such as proteins, labels, and otherchemical entities, to nucleotides are known in the art. Some newcross-linking reagents such as n-maleimidobutyryloxy-succinimide ester(GMBS) and sulfo-GMBS, have reduced immunogenicity. Substituents havebeen attached to the 5′ end of preconstructed oligonucleotides usingamidite or H-phosphonate chemistry, as described by Ogilvie, K. K., etal., Pure and Appl Chem (1987) 59:325, and by Froehler, B. C., NucleicAcids Res (1986) 14:5399, both of which are incorporated herein byreference. Substituents have also been attached to the 3′ end ofoligomers, as described by Asseline, U., et al., Tet Left (1989)30:2521, incorporated herein by reference. This last method utilizes2,2′-dithioethanol attached to a solid support to displacediisopropylamine from a 3′ phosphonate bearing the acridine moiety andis subsequently deleted after oxidation of the phosphorus. Othersubstituents have been bound to the 3′ end of oligomers by alternatemethods, including polylysine (Bayard, B., et al., Biochemistry (1986)25:3730; Lemaitre, M., et al., Nucleosides and Nucleotides (1987) 6:311,both of which are incorporated herein by reference) and, in addition,disulfides have been used to attach various groups to the 3′ terminus,as described by Zuckerman, R., et al., Nucleic Acids Res (1987) 15:5305,incorporated herein by reference. It is known that oligonucleotideswhich are substituted at the 3′ end show increased stability andincreased resistance to degradation by exonucleases (Lancelot, G., etal., Biochemistry (1985) 24:2521; Asseline, U., et al., Proc Natl AcedSci USA (1984) 81:3297, both of which are incorporated herein byreference). Additional methods of attaching non-nucleotide entities tooligonucleotides are discussed in U.S. Pat. Nos. 5,321,131 and5,414,077.

Alternatively, an oligonucleotide may include one or more modifiednucleotides having a group attached via a linker arm to the base. Forexample, Langer et al (Proc. Natl. Acad. Sci. U.S.A., 78(11):6633-6637,1981, incorporated herein by reference) describes the attachment ofbiotin to the C-5 position of dUTP by an allylamine linker arm. Theattachment of biotin and other groups to the 5-position of pyrimidinesvia a linker arm is also discussed in U.S. Pat. No. 4,711,955.Nucleotides labeled via a linker arm attached to the 5- or otherpositions of pyrimidines are also suggested in U.S. Pat. No. 4,948,882.Bisulfite-catalyzed transamination of the N.sup.4-position of cytosinewith bifunctional amines is described by Schulman et al. (Nucleic AcidsResearch, 9(5): 1203-1217, 1981) and Draper et al (Biochemistry, 19:1774-1781, 1980, incorporated herein by reference). By this method,chemical entities are attached via linker arms to cytidine orcytidine-containing polynucleotides. The attachment of biotin to theN4-position of cytidine is disclosed in U.S. Pat. No. 4,828,979,incorporated herein by reference, and the linking of moieties tocytidine at the N⁴-position is also set forth in U.S. Pat. Nos.5,013,831 and 5,241,060, both of which are incorporated herein byreference. U.S. Pat. No. 5,407,801, incorporated herein by reference,describes the preparation of an oligonucleotide triplex wherein a linkerarm is conjugated to deoxycytidine via bisulfite-catalyzedtransamination. The linker arms include an aminoalkyl or carboxyalkyllinker arm. U.S. Pat. No. 5,405,950, incorporated herein by reference,describes cytidine analogs in which a linker arm is attached to theN4-position of the cytosine base.

Numerous cross-linking reagents, including the ones discussed above, arecommercially available. Detailed instructions for their use are readilyavailable from the commercial suppliers. A general reference on proteincross-linking and conjugate preparation is: S. S. Wong, Chemistry ofProtein Conjugation and Cross-Linking, CRC Press (1991), incorporatedherein by reference.

Chemical cross-linking may include the use of spacer arms, i.e., linkersor tethers. Spacer arms provide intramolecular flexibility or adjustintramolecular distances between conjugated moieties and thereby mayhelp preserve biological activity. A spacer arm may be in the form of apeptide moiety comprising spacer amino acids. Alternatively, a spacerarm may be part of the cross-linking reagent, such as in “long-chainSPDP” (Pierce Chem. Co., Rockford, Ill., cat. No. 21651H), incorporatedherein by reference.

A variety of coupling or crosslinking agents such as protein A,carbodiimide, dimaleimide, dithio-bis-nitrobenzoic acid (DTNB),N-succinimidyl-S-acetyl-thioacetate (SATA), andN-succinimidyl-3-(2-pyrid-yldithio) propionate (SPDP),6-hydrazinonicotimide (HYNIC), N₃S and N₂S₂ can be used in well-knownprocedures to synthesize targeted constructs. For example, biotin can beconjugated to an oligonucleotide via DTPA using the bicyclic anhydridemethod of Hnatowich et al. Int. J. Appl. Radiat. Isotop. 33:327 (1982),incorporated herein by reference.

In addition, sulfosuccinimidyl 6-(biotinamido)hexanoate (NHS-LC-biotin,which can be purchased from Pierce Chemical Co. Rockford, Ill.),“biocytin,” a lysine conjugate of biotin, can be useful for makingbiotin compounds due to the availability of a primary amine. Inaddition, corresponding biotin acid chloride or acid precursors can becoupled with an amino derivative of the therapeutic agent by knownmethods. By coupling a biotin moiety to the surface of a particle,another moiety may be coupled to avidin and then coupled to the particleby the strong avidin-biotin affinity, or vice versa.

Analogous methods can also be used to link a surface-altering agent to asmall molecule, protein, or other substance in need of suchmodification.

In certain embodiments where a particle comprises PEG moieties on thesurface of the particle, the free hydroxyl group of PEG may be used forlinkage or attachment (e.g., covalent attachment) of additionalmolecules or moieties to the particle.

Imaging labels may be coupled to a particle by covalent bonding directlyor indirectly to an atom of the polymer or surface-altering agent, orthe label may be non-covalently or covalently associated with theparticle through a chelating structure or through an auxiliary moleculesuch as mannitol, gluconate, glucoheptonate, tartrate, and the like.

Any suitable chelating structure may be used to provide spatialproximity between a radionuclide and the particle through covalent ornoncovalent association. Many such chelating structures are known in theart. Preferably, the chelating structure is an N₂S₂ structure, an N₃Sstructure, an N₄ structure, an isonitrile-containing structure, ahydrazine containing structure, a HYNIC (hydrazinonicotinicacid)-containing structure, a 2-methylthionicotinic acid-containingstructure, a carboxylate-containing structure, or the like. In somecases, chelation can be achieved without including a separate chelatingstructure, because the radionuclide chelates directly to atom(s) in orpendant from the particle, for example to oxygen atoms in the polymer ora polyethylene glycol surface-altering agent.

Radionuclides may be placed in spatial proximity to a particle usingknown procedures which effect or optimize chelation, association, orattachment of the specific radionuclide to a component of the particleor a moiety pendant from the particle's surface. For example, when ¹²³Iis the radionuclide, the imaging agent may be labeled in accordance withthe known radioiodination procedures such as direct radioiodination withchloramine T, radioiodination exchange for a halogen or anorganometallic group, and the like. When the radionuclide is ⁹⁹mTc, theimaging agent may be labeled using any method suitable for attaching⁹⁹mTc to a ligand molecule. Preferably, when the radionuclide is ⁹⁹mTc,an auxiliary molecule such as mannitol, gluconate, glucoheptonate, ortartrate is included in the labeling reaction mixture, with or without achelating structure. More preferably, ⁹⁹mTc is placed in spatialproximity to the targeting molecule by reducing ⁹⁹mTcO₄ with tin in thepresence of mannitol and the targeting molecule. Other reducing agents,including tin tartrate or non-tin reductants such as sodium dithionite,may also be used to make an imaging agent according to the invention.

In general, labeling methodologies vary with the choice of radionuclide,the moiety to be labeled and the clinical condition under investigation.Labeling methods using ⁹⁹mTc and ¹¹¹In are described for example inPeters, A. M. et al., Lancet 2: 946-949 (1986); Srivastava, S. C. etal., Semin. Nucl. Med. 14(2):68-82 (1984); Sinn, H. et al, Nucl. Med.(Stuttgart) 13:180, 1984); McAfee, J. O. et al., J. Nucl. Med.17:480-487, 1976; McAfee, J. G. et al., J. Nucl. Med. 17:480-487, 1976;Welch, M. J. et al., J. Nucl. Med. 18:558-562, 1977; McAfee, J. G., etal., Semin. Nucl. Med. 14(2):83, 1984; Thakur, M. L., et al., Semin.Nucl. Med. 14(2):107, 1984; Danpure, H. J. et al., Br. J. Radiol.,54:597-601, 1981; Danpure, H. J. et al., Br. J. Radiol. 55:247-249,1982; Peters, A. M. et al., J. Nucl. Med. 24:39-44, 1982; Gunter, K. P.et al., Radiology 149:563-566, 1983; and Thakur, M. L. et al., J. Nucl.Med. 26:518-523, 1985, all of which are incorporated herein byreference.

Particles can be characterized using standard methods of high field NMRspectra as well as IR, MS, and optical rotation. Elemental analysis,TLC, and/or HPLC can be used as a measure of purity. A purity of atleast about 80%, preferably at least about 90%; more preferably at leastabout 95% and even more preferably at least about 98% is preferred. TLCand/or HPLC can also be used to characterize such compounds.

Once prepared, candidate particles can be screened for ability to carrytheir bioactive agent(s) across a mucosal barrier. The candidateparticles may also be tested for ability to transfect a cell, if thecarried bioactive agent is a nucleic acid. In addition, stability of aparticle can be tested by incubating the compound in serum, e.g., humanserum, and measuring the potential degradation of the compound overtime. Stability can also be determined by administering the compound toa subject (human or non-human), obtaining blood samples at various timeperiods (e.g., 30 min, 1 hour, 24 hours) and analyzing the blood samplesfor derived or related metabolites.

A “drug,” “therapeutic agent,” or “medicament,” is a biologically,physiologically, or pharmacologically active substance, that actslocally or systemically in the human or animal body. A subjectcomposition may include any active substance.

Various forms of the medicaments or drug may be used which are capableof being carried by the particles across mucosal barriers into adjacenttissues or fluids. They may be acidic, basic, or salts. They may beneutral molecules, polar molecules, or molecular complexes capable ofhydrogen bonding. They may be in the form of ethers, esters, amides andthe like, including prodrugs which are biologically activated wheninjected into the human or animal body, e.g., by cleavage of an ester oramide. An analgesic agent is also an example of a “medicament.” Anyadditional medicament in a subject composition may vary widely with thepurpose for the composition. The term “medicament” includes withoutlimitation, vitamins; mineral supplements; substances used for thetreatment, prevention, diagnosis, cure or mitigation of disease orillness; substances which affect the structure or function of the body;or pro-drugs, which become biologically active or more active after theyhave been placed in a predetermined physiological environment.

Plasticizers and stabilizing agents known in the art may be incorporatedin particles of the present invention. In certain embodiments, additivessuch as plasticizers and stabilizing agents are selected for theirbiocompatibility. In certain embodiments, the additives are lungsurfactants, such as 1,2-dipalmitoylphosphatidycholine (DPPC) andL-α-phosphatidylcholine (PC).

In other embodiments, spheronization enhancers facilitate the productionof subject particles that are generally spherical in shape. Substancessuch as zein, microcrystalline cellulose or microcrystalline celluloseco-processed with sodium carboxymethyl cellulose may confer plasticityto the subject compositions as well as impart strength and integrity. Inparticular embodiments, during spheronization, extrudates that arerigid, but not plastic, result in the formation of dumbbell shapedparticles and/or a high proportion of fines, and extrudates that areplastic, but not rigid, tend to agglomerate and form excessively largeparticles. In such embodiments, a balance between rigidity andplasticity is desirable. The percent of spheronization enhancer in aformulation typically range from 10 to 90% (w/w). In certainembodiments, a subject composition includes an excipient. A particularexcipient may be selected based on its melting point, solubility in aselected solvent (e.g., a solvent that dissolves the polymer and/or thetherapeutic agent), and the resulting characteristics of the particles.

Excipients may make up a few percent, about 5%, 10%, 15%, 20%, 25%, 30%,40%, 50%, or higher percentage of the subject compositions.

Buffers, acids and bases may be incorporated in the subject compositionsto adjust their pH. Agents to increase the diffusion distance of agentsreleased from the polymer matrix may also be included.

4. Applications: Therapeutic and Diagnostic Compositions

In part, a polymer particle of the present invention includes abiocompatible and preferably biodegradable polymer, such as any polymerdiscussed above, optionally including any other biocompatible andoptionally biodegradable polymer mentioned above or known in the art.The invention provides pharmaceutical compositions that include one ormore particles. A pharmaceutical composition may be a therapeuticcomposition and/or a diagnostic or imaging composition.

A. Physical Structures of the Subject Compositions

The subject particles, e.g., microparticles or preferably nanoparticles,may comprise polymeric matrices. Microparticles typically comprise abiodegradable polymer matrix and a bioactive agent, e.g., the bioactiveagent is encapsulated by or adsorbed to the polymer matrix.Microparticles can be formed by a wide variety of techniques known tothose of skill in the art. Examples of microparticle-forming techniquesinclude, but are not limited to, (a) phase separation by emulsificationand subsequent organic solvent evaporation (including complex emulsionmethods such as oil-in-water emulsions, water-in-oil emulsions, andwater-oil-water emulsions); (b) coacervation-phase separation; (c) meltdispersion; (d) interfacial deposition; (e) in situ polymerization; (1)spray-drying and spray-congealing; (g) air suspension coating; and (h)pan and spray coating. These methods, as well as properties andcharacteristics of microparticles are disclosed in, for example, U.S.Pat. Nos. 4,652,441; 5,100,669; 4,526,938; WO 93/24150; EPA 0258780 A2;U.S. Pat. Nos. 4,438,253; and 5,330,768, the entire disclosures of whichare incorporated by reference herein.

To prepare particles of the present invention, several methods can beemployed depending upon the desired application of the deliveryvehicles. Suitable methods include, but are not limited to,spray-drying, freeze-drying, air drying, vacuum drying, fluidized-beddrying, milling, co-precipitation and critical fluid extraction. In thecase of spray-drying, freeze-drying, air drying, vacuum drying,fluidized-bed drying and critical fluid extraction; the components(stabilizing polyol, bioactive material, buffers, etc.) are firstdissolved or suspended in aqueous conditions. In the case ofco-precipitation, the components are mixed in organic conditions andprocessed as described below. Spray-drying can be used to load theparticle with the bioactive material. The components are mixed underaqueous conditions and dried using precision nozzles to produceextremely uniform droplets in a drying chamber. Suitable spray dryingmachines include, but are not limited to, Buchi, NIRO, APV and Lab-plantspray driers used according to the manufacturer's instructions.

The shape of microparticles and nanoparticles may be determined byscanning or transmission electron microscopy. Spherically shapednanoparticles are used in certain embodiments, e.g., for circulationthrough the bloodstream. If desired, the particles may be fabricatedusing known techniques into other shapes that are more useful for aspecific application.

In addition to intracellular delivery of a therapeutic agent, it alsopossible that particles of the subject compositions, such asmicroparticles or nanoparticles, may undergo endocytosis, therebyobtaining access to the cell. The frequency of such, an endocytosisprocess will likely depend on the size of any particle.

B. Dosages and Formulations of the Subject Compositions

In most embodiments, the subject polymers will incorporate the substanceto be delivered in an amount sufficient to deliver to a patient atherapeutically effective amount of an incorporated therapeutic agent orother material as part of a diagnostic, prophylactic, or therapeutictreatment. The desired concentration of active compound in the particlewill depend on absorption, inactivation, and excretion rates of the drugas well as the delivery rate of the compound from the subjectcompositions. It is to be noted that dosage values may also vary withthe severity of the condition to be alleviated. It is to be furtherunderstood that for any particular subject, specific dosage regimensshould be adjusted over time according to the individual need and theprofessional judgment of the person administering or supervising theadministration of the compositions. Typically, dosing will be determinedusing techniques known to one skilled in the art.

Further, the amounts of bioactive substances will vary depending uponthe relative potency of the agents selected. Additionally, the optimalconcentration and/or quantities or amounts of any particular therapeuticagent may be adjusted to accommodate variations in the treatmentparameters. Such treatment parameters include the polymer composition ofa particular preparation, the identity of the therapeutic agentutilized, and the clinical use to which the preparation is put, e.g.,the site treated, the type of patient, e.g., human or non-human, adultor child, and the nature of the disease or condition.

The concentration and/or amount of any therapeutic agent or otheradsorbed or encapsulated material for a given subject composition mayreadily identified by routine screening in animals, e.g., rats, byscreening a range of concentration and/or amounts of the material inquestion using appropriate assays. Known methods are also available toassay local tissue concentrations, diffusion rates from particles andlocal blood flow before and after administration of therapeuticformulations according to the invention, One such method ismicrodialysis, as reviewed by T. E. Robinson et al., 1991, MICRODIALYSISIN THE NEUROSCIENCES, Techniques, volume 7, Chapter 1. The methodsreviewed by Robinson may be applied, in brief, as follows. Amicrodialysis loop is placed in situ in a test animal, Dialysis fluid ispumped through the loop. When particles according to the invention areinjected adjacent to the loop, released drugs are collected in thedialysate in proportion to their local tissue concentrations. Theprogress of diffusion of the active agents may be determined therebywith suitable calibration procedures using known concentrations ofactive agents.

In certain embodiments, the dosage of the subject invention may bedetermined by reference to the plasma concentrations of the therapeuticagent or other encapsulated materials. For example, the maximum plasmaconcentration (C_(max)) and the area under the plasma concentration-timecurve from time 0 to infinity may be used.

The compositions of the present invention may be administered by variousmeans, depending on their intended use, as is well known in the art. Forexample, if subject compositions are to be administered orally, it maybe formulated as tablets, capsules, granules, powders or syrups.Alternatively, formulations of the present invention may be administeredparenterally as injections (intravenous, intramuscular, orsubcutaneous), drop infusion preparations, or suppositories. Forapplication by the ophthalmic mucous membrane route, subjectcompositions may be formulated as eyedrops or eye ointments. Theseformulations may be prepared by conventional means, and, if desired, thesubject compositions may be mixed with any conventional additive, suchas a binder, a disintegrating agent, a lubricant, a corrigent, asolubilizing agent, a suspension aid, an emulsifying agent or a coatingagent.

In addition, in certain embodiments, subject compositions of the presentinvention maybe lyophilized or subjected to another appropriate dryingtechnique such as spray drying.

The subject compositions may be administered once, or may be dividedinto a number of smaller doses to be administered at varying intervalsof time, depending in part on the release rate of the compositions andthe desired dosage.

Formulations useful in the methods of the present invention includethose suitable for oral, nasal, topical (including buccal andsublingual), rectal, vaginal, aerosol and/or parenteral administration.The formulations may conveniently be presented in unit dosage form andmay be prepared by any methods well known in the art of pharmacy. Theamount of a subject composition which may be combined with a carriermaterial to produce a single dose may vary depending upon the subjectbeing treated, and the particular mode of administration.

Methods of preparing these formulations or compositions include the stepof bringing into association subject compositions with the carrier and,optionally, one or more accessory ingredients. In general, theformulations are prepared by uniformly and intimately bringing intoassociation a subject composition with liquid carriers, or finelydivided solid carriers, or both, and then, if necessary, shaping theproduct.

Particles, particularly nanoparticles, which may be administered ininhalant or aerosol formulations according to the invention comprise oneor more agents, such as adjuvants, diagnostic agents, imaging agents, ortherapeutic agents useful in inhalation therapy.

The particle size of the particulate medicament should be such as topermit inhalation of substantially all of the medicament into the lungsupon administration of the aerosol formulation and will thus desirablybe less than 20 microns, preferably in the range 1 to 10 microns, e.g.,1 to 5 microns. The particle size of the medicament may be reduced byconventional means, for example by milling or micronisation.

The final aerosol formulation desirably contains 0.005-90% w/w,preferably 0.005-50%, more preferably 0.005-5% w/w, especially 0.01-1.0%w/w, of medicament relative to the total weight of the formulation.

It is desirable, but by no means required, that the formulations of theinvention contain no components which may provoke the degradation ofstratospheric ozone. In particular it is desirable that the formulationsare substantially free of chlorofluorocarbons such as CCl₃F, CCl₂F₂ andCF₃CCl₃. As used herein “substantially lree” means less than 1% w/wbased upon the propellant system, in particular less than 0.5%, forexample 0.1% or less.

The propellant may optionally contain an adjuvant having a higherpolarity and/or a higher boiling point than the propellant. Polaradjuvants which may be used include (e.g., C₂₋₆) aliphatic alcohols andpolyols such as ethanol, isopropanol and propylene glycol, preferablyethanol. In general, only small quantities of polar adjuvants (e.g.,0.05-3.0% w/w) may be required to improve the stability of thedispersion—the use of quantities in excess of 5% w/w may tend todissolve the medicament. Formulations in accordance with the inventionmay preferably contain less than 1% w/w, e.g., about 0.1% w/w, of polaradjuvant. However, the formulations of the invention are preferablysubstantially free of polar adjuvants, especially ethanol. Suitablevolatile adjuvants include saturated hydrocarbons such as propane,n-butane, isobutane, pentane and isopentane and alkyl ethers such asdimethyl ether. In general, up to 50% w/w of the propellant may comprisea volatile adjuvant, for example 1 to 30% w/w of a volatile saturatedC1-C6 hydrocarbon.

Optionally, the aerosol formulations according to the invention mayfurther comprise one or more surfactants. The surfactants must bephysiologically acceptable upon administration by inhalation. Withinthis category are included surfactants such as L-α-phosphatidylcholine(PC), 1,2-dipalmitoylphosphatidycholine (DPPC), oleic acid, sorbitantrioleate, sorbitan mono-oleate, sorbitan monolaurate, polyoxyethylene(20) sorbitan monolaurate, polyoxyethylene (20) sorbitan monooleate,natural lecithin, oleyl polyoxyethylene (2) ether, stearylpolyoxyethylene (2) ether, lauryl polyoxyethylene (4) ether, blockcopolymers of oxyethylene and oxypropylene, synthetic lecithin,diethylene glycol dioleate, tetrahydrofurfuryl oleate, ethyl oleate,isopropyl myristate, glyceryl monooleate, glyceryl monostearate,glyceryl monoricinoleate, cetyl alcohol, stearyl alcohol, polyethyleneglycol 400, cetyl pyridinium chloride, benzalkonium chloride, olive oil,glyceryl monolaurate, corn oil, cotton seed oil, and sunflower seed oil.Preferred surfactants are lecithin, oleic acid, and sorbitan trioleate.

The formulations of the invention may be prepared by dispersal of theparticles in the selected propellant and/or co-propellant in anappropriate container, e.g., with the aid of sonication. Preferably, theparticles are suspended in co-propellant and filled into a suitablecontainer. The valve of the container is then sealed into place and thepropellant introduced by pressure filling through the valve in theconventional manner. The particles may be thus suspended or dissolved ina liquified propellant, sealed in a container with a metering valve andfitted into an actuator. Such metered dose inhalers are well known inthe art. The metering valve may meter 10 to 500 μL and preferably 25 to150 μL. In certain embodiments, dispersal may be achieved using drypowder inhalers (e.g., spinhaler) for the particles (which remain as drypowders). In other embodiments, nanospheres, may be suspended in anaqueous fluid and nebulized into fine droplets to be aerosolized intothe lungs.

Sonic nebulizers may be used because they minimize exposing the agent toshear, which may result in degradation of the particles. Ordinarily, anaqueous aerosol is made by formulating an aqueous solution or suspensionof the particles together with conventional pharmaceutically acceptablecarriers and stabilizers. The carriers and stabilizers vary with therequirements of the particular composition, but typically includenon-ionic surfactants (Tweens, Pluronics, or polyethylene glycol),innocuous proteins like serum albumin, sorbitan esters, oleic acid,lecithin, amino acids such as glycine, buffers, salts, sugars, or sugaralcohols. Aerosols generally are prepared from isotonic solutions.

Ophthalmic formulations, eye ointments, powders, solutions and the like,are also contemplated as being within the scope of this invention.

Certain pharmaceutical compositions of this invention suitable forparenteral administration comprise one or more subject compositions incombination with one or more pharmaceutically acceptable sterile,isotonic, aqueous, or non-aqueous solutions, dispersions, suspensions oremulsions, or sterile powders which may be reconstituted into sterileinjectable solutions or dispersions just prior to use, which may containantioxidants, buffers, bacteriostats, solutes which render theformulation isotonic with the blood of the intended recipient orsuspending or thickening agents.

Examples of suitable aqueous and non-aqueous carriers which may beemployed in the pharmaceutical compositions of the invention includewater, ethanol, polyols (such as glycerol, propylene glycol,polyethylene glycol, and the like), and suitable mixtures thereof,vegetable oils, such as olive oil, and injectable organic esters, suchas ethyl oleate. Proper fluidity may be maintained, for example, by theuse of coating materials, such as lecithin, by the maintenance of therequired particle size in the case of dispersions, and by the use ofsurfactants.

Microparticle and/or nanoparticle compositions may be suspended in apharmaceutically acceptable solution, such as saline, Ringer's solution,dextran solution, dextrose solution, sorbitol solution, a solutioncontaining polyvinyl alcohol (from about 1% to about 3%, preferablyabout 2%), or an osmotically balanced solution comprising a surfactant(such as Tween 80 or Tween 20) and a viscosity-enhancing agent (such asgelatin, alginate, sodium carboxymethylcellulose, etc.). In certainembodiments, the composition is administered subcutaneously. In otherembodiments, the composition is administered intravenously. Forintravenous delivery, the composition is preferably formulated asmicroparticles or nanoparticles on average less than about 15 microns,more particularly less than about 10 microns, more particularly lessthan about 5 microns, and still more particularly less than about 5microns in average diameter.

Formulations suitable for oral administration may be in the form ofcapsules, cachets, pills, tablets, lozenges (using a flavored basis,usually sucrose and acacia or tragacanth), powders, granules, or as asolution or a suspension in an aqueous or non-aqueous liquid, or as anoil-in-water or water-in-oil liquid emulsion, or as an elixir or syrup,or as pastilles (using an inert base, such as gelatin and glycerin, orsucrose and acacia), each containing a predetermined amount of a subjectcomposition as an active ingredient. Subject compositions of the presentinvention may also be administered as a bolus, electuary, or paste.

In solid dosage forms for oral administration (capsules, tablets, pills,dragees, powders, granules and the like), the subject composition ismixed with one or more pharmaceutically acceptable carriers and/or anyof the following: (1) fillers or extenders, such as starches, lactose,sucrose, glucose, mannitol, and/or silicic acid; (2) binders, such as,for example, carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidone, sucrose and/or acacia; (3) humectants, such as glycerol;(4) disintegrating agents, such as agar-agar, calcium carbonate, potatoor tapioca starch, alginic acid, certain silicates, and sodiumcarbonate; (5) solution retarding agents, such as paraffin; (6)absorption accelerators, such as quaternary ammonium compounds; (7)wetting agents, such as, for example, acetyl alcohol and glycerolmonostearate; (8) absorbents, such as kaolin and bentonite clay; (9)lubricants, such a talc, calcium stearate, magnesium stearate, solidpolyethylene glycols, sodium lauryl sulfate, and mixtures thereof; and(10) coloring agents. In the case of capsules, tablets and pills, thepharmaceutical compositions may also comprise buffering agents. Solidcompositions of a similar type may also be employed as fillers in softand hard-filled gelatin capsules using lactose or milk sugars, as wellas high molecular weight polyethylene glycols and the like.

A tablet may be made by compression or molding, optionally with one ormore accessory ingredients. Compressed tablets may be prepared using abinder (for example, gelatin or hydroxypropylmethyl cellulose),lubricant, inert diluent, preservative, disintegrant (for example,sodium starch glycolate or cross-linked sodium carboxymethyl cellulose),surface-altering or dispersing agent. Molded tablets may be made bymolding in a suitable machine a mixture of the subject compositionmoistened with an inert liquid diluent. Tablets, and other solid dosageforms, such as dragees, capsules, pills and granules, may optionally bescored or prepared with coatings and shells, such as enteric coatingsand other coatings well known in the pharmaceutical-formulating art.

Liquid dosage forms for oral administration include pharmaceuticallyacceptable emulsions, microemulsions, solutions, suspensions, syrups andelixirs. In addition to the subject compositions, the liquid dosageforms may contain inert diluents commonly used in the art, such as, forexample, water or other solvents, solubilizing agents and emulsifiers,such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethylacetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butyleneglycol, oils (in particular, cottonseed, corn, peanut, sunflower,soybean, olive, castor, and sesame oils), glycerol, tetrahydrofurylalcohol, polyethylene glycols and fatty acid esters of sorbitan, andmixtures thereof.

Suspensions, in addition to the subject compositions, may containsuspending agents such as, for example, ethoxylated isostearyl alcohols,polyoxyethylene sorbitol, and sorbitan esters, microcrystallinecellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth,and mixtures thereof.

Formulations for rectal or vaginal administration may be presented as asuppository, which may be prepared by mixing a subject composition withone or more suitable non-irritating carriers comprising, for example,cocoa butter, polyethylene glycol, a suppository wax, or a salicylate,and which is solid at room temperature, but liquid at body temperatureand, therefore, will melt in the appropriate body cavity and release theencapsulated particles. An exemplary formulation for vaginaladministration may comprise a bioactive agent that is a contraceptive oran anti-viral, anti-fungal or antibiotic agent.

Formulations which are suitable for vaginal administration also includepessaries, tampons, creams, gels, pastes, foams, or spray formulationscontaining such carriers as are known in the art to be appropriate.

Dosage forms for transdermal administration include powders, sprays,ointments, pastes, creams, lotions, gels, solutions, patches, andinhalants. A subject composition may be mixed under sterile conditionswith a pharmaceutically acceptable carrier, and with any preservatives,buffers, or propellants that may be required. For transdermaladministration, the complexes may include lipophilic and hydrophilicgroups to achieve the desired water solubility and transport properties.

The ointments, pastes, creams and gels may contain, in addition tosubject compositions, other carriers, such as animal and vegetable fats,oils, waxes, paraffins, starch, tragacanth, cellulose derivatives,polyethylene glycols, silicones, bentonites, silicic acid, talc and zincoxide, or mixtures thereof. Powders and sprays may contain, in additionto a subject composition, excipients such as lactose, talc, silicicacid, aluminum hydroxide, calcium silicates and polyamide powder, ormixtures of such substances. Sprays may additionally contain customarypropellants, such as chlorofluorohydrocarbons and volatile unsubstitutedhydrocarbons, such as butane and propane.

Exemplification

The invention now being generally described, it will be more readilyunderstood by reference to the following examples, which are includedmerely for purposes of illustration of certain aspects and embodimentsof the present invention, and are not intended to limit the invention.

1. Materials and Methods

1.1 Cervicovaginal and Cystic Fibrosis Mucus Collection and Preparation

The cervicovaginal mucus collection procedure was performed as publishedpreviously (Boskey, E R. Moench, T R, Flees, P S & Cone, R A (2003)Sexually Transmitted Diseases 30, 107-109, incorporated herein byreference). Collected mucus was used for microscopy within 4 h. Theviscosity of fresh samples was observed as a function of shear rate at37° C. in a Brookfield cone and plate viscometer (Model HADV-III withCP-40 spindle; Brookfield Engineering Lab, Middleboro. Mass.).

Human respiratory sputum was expectorated from male and female CFpatients (ages 18-35). CF sputum samples from multiple patients werepooled, freeze-dried, and reconstituted in sputum buffer by stirring at4° C. to attain a large volume of homogeneous CF sputum. The volume ofsputum buffer added to reconstituted CF sputum samples was determined bymass measurements (the reconstituted CF sputum had the equivalent massof the fresh CF sputum samples).

1.2 Nanoparticle Preparation and Characterization

100-500 nm yellow-green fluorescent, carboxyl-modified polystyrene (PS)particles (Molecular Probes, Eugene, Oreg.) were covalently modifiedwith diamine PEG (MW ˜2 kDa; Nektar Therapeutics, San Carlos, Calif.)via carboxyl-amine reaction in 3:1 excess following manufacturersuggested protocol. Di-amine polyethylene glycol (PEG) of molecularweight 3,400 daltons (Nektar Therapeutics, San Carlos, Calif.) wasdissolved in 50 mM 2-(N-morpholino)ethanesulfonic acid (MES, Sigma, StLouis, Mo.) buffer at pH 6.0. The use of di-amine PEG may result in afree amine group at the end of the surface-bound PEG chains.Yellow-green fluorescent polystyrene nanospheres (Molecular Probes,Eugene, Oreg.) were added to the solution to give final concentrationsof 10 mg PEG/ml and 1% solids/ml. The nanospheres had diameters of 100nm and were carboxyl-modified. Following a 15 min incubation at roomtemperature, EDAC (1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide)(Sigma, St Louis, Mo.) was added to the mixture to a concentration of 4mg/ml. The pH of the solution was adjusted to 6.5 with dilute NaOH andincubated on an orbital shaker for 2 h at room temperature. To quenchthe reaction, glycine (JT Baker, Phillipsburg, N.J.) was added to give afinal concentration of 100 mM. The solution was incubated for 30 min atroom temperature and subsequently dialyzed extensively againstDulbecco's phosphate-buffered saline (PBS) in a 300,000 kDa MWCOFloat-a-lyzer (Spectrum Laboratories, Rancho Dominguez, Calif.).Unmodified microspheres were dialyzed similarly to remove all traces ofsodium azide originally added by the manufacturer.

The size and ξ-potential were determined by dynamic light scattering andlaser Doppler anemometry, respectively, using a Zetasizer 3000 (MalvernInstruments, Southborough, Mass.). Size measurements were performed at25° C. at a scattering angle of 90°. Samples were diluted in doubledistilled water and measurements performed according to instrumentinstructions.

1.3 Protein Adsorption to Particles—Measure of PEGylation Effectiveness

To confirm PEG attachment and quantify efficiency in resisting proteinadsorption by PEG, 10 μL of COOH-particles and PEG-modified particles(˜0.04% by mass) were added to 200 μL 0.1 mg/mL rhodamine fluorescentNeutrAvidin (Molecular Probes, Eugene, Oreg.) and incubated on anorbital shaker for 1 hour. Particles were subsequently washed twice inPBS, resuspended to a final concentration of 0.008% by mass, andobserved on sealed glass slides/coverslips using a confocal microscope(Zeiss LSM 510, Carl Zeiss Inc., Thornwood, N.Y.) equipped with a100×/1.4 NA oil-immersion lens. Samples were excited with 488 and 543lasers, and the pinhole was adjusted to obtain optical slices rangingfrom less than 0.7-0.8 μm. Identical excitation and detection settingswere maintained and all samples were tested sequentially. Particleswithout avidin incubation served as negative control to ensurenegligible bleach over. Maximum pixel intensity for each particle, afterconversion to grey scale, was analyzed using SCION image 4.03b.

1.4 Multiple Particle Tracking (MPT) in Cervicovaginal Mucus and CFMucus

Particle transport rates were measured by analyzing trajectories offluorescent particles, recorded using a silicon-intensified targetcamera (VE-1000, Dage-MTI, Michigan, Ind.) mounted on an invertedepifluorescence microscope equipped with 100×oil-immersion objective(numerical aperture 1.3). Experiments were carried out in 8-well glasschambers (LabTek, Campbell, Calif.) where diluted particle solutions(0.0082% w/v) were added to 250-500 μL of fresh mucus to a finalconcentration of 3% v/v (final particle conc 8.25×10⁻⁷ w/v) andincubated for 2 h prior to microscopy. Trajectories of n>100 particleswere analyzed for each experiment and three experiments were performedfor each condition. Movies were captured with Metamorph software(Universal Imaging Corp.) at a temporal resolution of 66.7 ms for 20 s.The tracking resolution was 10 nm, determined by tracking displacementsof particles immobilized with a strong adhesive. The coordinates ofnanoparticle centroids were transformed into time-averaged mean squareddisplacements (MSD), <Δr²(τ)>=[x(t+τ)−x(t)]²+[y(t+τ)−y(t)]² (τ=timescale or time lag), from which distributions of MSDs and effectivediffusivities were calculated, as previously demonstrated (Dawson, M,Wirtz, D & Hanes, J (2003) Journal of Biological Chemistry 278,50393-50401, Valentine, M T, Perlman, Z E, Gardel, M L, Shin, J H,Matsudaira, P, Mitchison, T J & Weitz, D A (2004) Biophys J 86, 4004-14,Mason, T G, Ganesan, K, vanZanten, J H, Wirtz, D & Kuo, S C (1997)Physical Review Letters 79, 3282-3285, all of which are incorporatedherein by reference). Additional information for measuring 3D transportby 2D particle tracking is provided in a recent review (Suh, J. Dawson,M & Hanes, J (2005) Adv Drug Deliv Rev 57, 63-78, incorporated herein byreference).

The time-dependent mean square displacements (MSD) of hundreds ofPEG-modified 500 nm polystyrene (PS-PEG) particles (0.5% by volume of a1:20 dilution of 2% particle solution) in CF sputum were determined bymultiple particle tracking (MPT). Mucus samples (200 μL) werecentrifuged and a portion of the supernatant (40 μL) was replaced withmucolytic solution or PBS to maintain the initial concentration of mucussolids and eliminate any dilution effects. The displacements ofparticles in the no treatment (PBS) control were identical to that ofparticles embedded in an unprocessed mucus sample, which was notcentrifuged. The tracking resolution, evaluated by tracking 500 nmpolystyrene probes in glycerol, was 5 nm.

1.5 Particle Transport Mode Classification

The mechanism of particle transport over short and long time scales wasclassified based on the concept of relative change (RC) of effectivediffusivity (D_(eff)). In brief, RC values of particles at short andlong time scales were calculated by dividing the D_(eff) of a particleat a probed time scale by the D_(eff) at an earlier reference timescale. By calculating RC values for two time regimes (i.e., short andlong time scales), one can obtain the transport mode that describes theparticle transport properties over different length and temporal scales.RC_(short) was defined at τ_(ref)=0.2 s and τ_(probe)=1 s, whereasRC_(long) was found at reference τ_(ref)=1 s and τ_(probe)=2 s. An RCstandard curve, which plots the 95% distribution range of D_(eff) forpurely Brownian particles over time scale, was generated based on MonteCarlo simulations and confirmed by tracking polystyrene nanoparticles inglycerol (data not shown). The transport modes of particles that displayRC values below the 97.5% range for either short or long time scaleswere classified as hindered, and the rest were classified as diffusive,Immobile particles are defined as those that display an average MSDsmaller than the 10-nm resolution at a time scale of 1 s. The rigor ofthe transport modes classification was confirmed by the slopes of theMSD vs. time scale plots, where diffusive particles possess a slope ofapproximately 1 and where the slope for hindered particles progressivelydecrease from 1 with increasing time scale.

2. Results and Discussion

2.1 Human Cervicovaginal Mucus and its Rheology.

Cervicovaginal (CV) mucus exhibits macroscopic viscosity within therange (in the higher end) of typical human mucus secretions, includinglungs, GI tract, nose, eyes and epididymus. This is partly attributed tothe similarity in their chemical composition. For example, the mucinglycoform MUC5B is the major secreted form of mucin in the mucosallayers protecting the CV tract, lungs, nose, and eye. The mucin content,approximately 1-3% by weight, is also similar between cervical, nasaland lung mucus. The composition of water in the aforementioned mucustypes all falls within the range of 90-98%.

2.2 Real-Time Transport of COOH-Modified Nanoparticles

We determined the effect of particle size on transport rates incervicovaginal (CV) mucus obtained from human volunteers. Thehydrodynamic diameters of the particles suspended in water,characterized by dynamic light scattering, are listed in FIG. 8 . Theaddition of uncoated particle at relatively high concentration (2%particles by weight) to CV mucus caused collapse of the mucus fibersinto bundles that trapped the particles and prevented their transport(data not shown). However, low concentration of particles (0.008%particles by weight) did not cause bundling and allowed particlemovement. As expected, particle transport was highly hindered by themucus mesh, evident from their low average mean square displacements(MSD) (FIG. 1A).

The ensemble-average effective diffusivity (D_(eff)) of COOH-PSparticles decreases at short time scales (FIG. 2B), as expected inmucus. By fitting particle MSD versus time scale (t) to the equationMSD=4D_(o)τ^(α), where D_(o) is the diffusion coefficient independent oftime scale, one can obtain an average value for a that provides insightinto the extent of impediment to particle motion (Note: α=1 for pureunobstructed Brownian diffusion, such as particles in water). Average αvalues were 0.16, 0.36 and 0.43 for 100, 200 and 500 nm COOH-PSparticles, respectively. Overall, the ensemble-average D_(eff) of 100,200 and 500 nm COOH-PS particles in mucus (at τ=1 s) were reduced by44000-, 590- and 4600-fold compared to the same particles in water (FIG.8 ).

To begin to understand the mechanistic reasons for the unexpectedly lowmobility of 100 nm COOH-PS particles (compared to 200 and 500 nm) acrossall time scales, we sorted particles based on their calculated Den (atx=1 s) into ten groups (FIG. 1C). Although the fastest 10% of 100 nmCOOH-PS particles had roughly similar D_(eff) as compared to 200 and 500nm COOH-PS particles, the mean D_(eff) values for 200 and 500 nm COOH-PSparticles were greater than that for 100 nm COOH-PS particles for allother subgroups (i.e., the slowest 90% of particles), which accounts forthe slower ensemble mobility of 100 nm COOH-PS particles. The Der ofindividual particles of all sizes spanned a wide range, with the fastestand slowest particles within each particle size differing by at least 4orders of magnitude (FIG. 1C).

2.3 Real-Time Transport of PEG-Modified Nanoparticles

Polyethylene glycol (PEG), a hydrophilic and uncharged polymer, wascovalently attached to the surface of 100, 200 and 500 nm particles inan attempt to reduce particle interactions with CV mucus. The extent ofPEG attachment was comparable for all particles, as shown by their nearneutral surface charges and similar efficiencies in resisting adsorptionof fluorescently labeled avidin (FIG. 8 ). PEGylation greatly increasedparticle transport rates, as evident by the 20, 400- and 1100-foldhigher ensemble MSDs (τ=1 s) of 100, 200 and 500 nm PEGylated particles(PEG-PS) compared to corresponding COOH-PS particles of the same size(FIG. 2A). The D_(eff) (τ=1 s) for 100 nm, 200 nm and 500 nm PEG-PSparticles were only reduced by 2000-, 6- and 4-fold compared to that ofthe expected values for their diffusion in water. The ensemble D_(eff)'s of PEG-PS particles of all three sizes still decreased withincreasing time scale (FIG. 2B), but only 100 nm PEG-PS particlesexperienced extensive obstruction to transport (α=0.31, 0.81, 0.89 for100, 200 and 500 nm PEG-PS particles, respectively). PEGylation not onlyreduced impediment for larger PEG-PS particles (200 and 500 nm), butalso increased the homogeneity of transport compared to similar sizedCOOH-PS particles (FIG. 2C).

The greatly improved transport rates upon PEGylation, especially forlarger particles, were largely due to a marked reduction in the fractionof mucoadhesive (immobile+hindered) particles (FIGS. 2D & 2E). Indeed, 2kDa PEG increased the fraction of mucus-penetrating (diffusive)particles to nearly 70% (FIG. 2F). This directly demonstrates thatnon-adhesive nanoparticles larger than the previously reported upperlimit of theoretical mesh size of mucus (200 nm) can undergo rapidtransport in human mucus.

2.4 Properties of Particles Coated with High M.W, (10 kDa) PEG

High MW PEG is widely used as a mucoadhesive agent (Bures, P., Y. Huang,E. Oral, and N. A. Peppas, Surface modifications and molecularimprinting of polymers in medical and pharmaceutical applications. JControl Release, 2001. 72(1-3): p. 25-33, Huang, Y., W. Leobandung, A.Foss, and N. A. Peppas, Molecular aspects of muco-and bioadhesion:tethered structures and site-specific surfaces. J Control Release, 2000.65(1-2): p. 63-71, Lele, B. S. and A. S. Hoffman, Mucoadhesive drugcarriers based on complexes of poly(acrylic acid) and PEGylated drugshaving hydrolysable PEG-anhydride-drug linkages. J Control Release,2000. 69(2): p. 237-48, Peppas, N. A., K. B. Keys, M. Torres-Lugo, andA. M. Lowman, Poly(ethylene glycol)-containing hydrogels in drugdelivery. J Control Release, 1999. 62(1-2): p. 81-7). To test its effectas a coating for nanoparticles, 10 kDa PEG was covalently attached tothe surface of 200 nm particles (PEG_(10kDa)-PS). In sharp contrast tothe PEG_(2kDa)-PS counterparts, particles having a dense coating of 10kDa PEG showed greatly reduced particle transport rates in fresh humanCV mucus, as evident by the 2300-fold lower ensemble MSDs (τ=1 s)compared to particles modified with 2 kDa PEG (FIG. 3A). In fact, theextensive obstruction to transport for PEG_(10kDa)-PS resulted in anensemble MSD (τ=1 s) nearly 6-fold lower than that for similar-sizedCOOH-PS particles, due in large part to the high fractions of bothimmobile and strongly hindered particles (i.e. mucoadhesive) (FIG. 3B).Without wishing to be bound by theory, it is possible that low MW PEGeliminates mucoadhesion by minimizing both hydrogen bonding andinterpenetration of PEG chains into the mucus gel, while higher MW PEG,with longer, flexible chains that extend farther from the surface of theparticle, penetrates into the mucus gel in a fashion that impedesdiffusion. Alternative approaches to modifying particles with high MWPEG, however, may control the length and flexibility of pendant PEGchains, thereby providing a mucus-resistant surface property.

2.5 N-Acetyl Cysteine Improves Nanoparticle Transport in Human CFSputum.

Mucus degrading agents, such as rhDNase (which hydrolyzes linear DNA)and N-acetyl-cysteine (NAC) (which cleaves disulphide and sulphahydrylbonds present in mucin), are used clinically to increase the rate ofmucus clearance (Hanes, J., M. Dawson, Y. Har-el, J. Suh, and J. Fiegel,Gene Delivery to the Lung. Pharmaceutical inhalation Aerosol Technology,A. J. Hickey, Editor. Marcel Dekker Inc.: New York, 2003: p. 489-539).These agents may also be valuable adjuvants in increasing the rate ofnanoparticle transport in mucus (Ferrari, S., C. Kitson, R. Farley, R.Steel, C. Marriott, D. A. Parkins, M. Scarpa, B. Wainwright, M. J.Evans, W. H. Colledge, D. M. Geddes, and E. W. Alton, Mucus alteringagents as adjuncts for nonviral gene transfer to airway epithelium. GeneTher, 2001. 8(18): p. 1380-6). Previously, we quantified the effect ofrhDNase on particle transport rates in CF mucus using multiple particletracking (FIG. 4 ). The distribution of individual particle transportrates was remarkably more homogeneous at 30 mins post-treatment withrhDNAse than in the no treatment control (compare FIGS. 4A and 4B).However, despite the reduction in bulk viscoelastic properties by morethan 50% (FIG. 4C), treatment with rhDNase actually reduced the overallensemble averaged transport rates of nanoparticles (FIG. 4D).Alternative approaches to treating mucus with rhDNAse, for exampledifferent incubation times and different buffers, may improve itsutility as a mucolytic agent. In contrast, treatment with NACsignificantly improved the transport rates of nanoparticles (FIG. 4E).

Ensemble geometric mean square displacements show that pretreatment ofmucus with neutralized N-acetyl-L-cysteine increased transport rates10.7-fold compared to no-treatment control (FIG. 5A). Classifying thetrajectories of particle motion into different transport modes(immobile, hindered, diffusive) show that the diffusive fraction of 500nm PEG-PS is enhanced 3-fold compared to the no-treatment control (FIG.5B).

2.6 Particle Trajectories

The typical trajectories of particles undergoing transport in CV mucuswere recorded and quantified by microscopy. Particles fall into threegeneral categories: immobile (FIG. 6A), hindered (FIG. 68 ), anddiffusive (FIG. 6C).

2.7 Quantification of PEG Surface Coating

Rapid transport by polymeric nanoparticles in undiluted human mucus islikely a direct consequence of improved surface coating of PEG.Previously, 500 nm PEG coated particles (as disclosed in Example 6B inWO 2005/072710 A2), with a low PEG density (Prep A, FIG. 7 ), were foundto improve transport ˜10-fold compared to uncoated particles of similarsize. In contrast, higher density of surface PEG (Prep B, FIG. 7 ) wasable to mediate improvements in transport of 500 nm particles by up to˜1100-fold compared to similar sized uncoated counterparts. Thisdirectly underscores the importance of high density of surface PEGcoating in dictating particle transport in mucus.

REFERENCES

All publications and patents mentioned herein, are hereby incorporatedby reference in their entirety as if each individual publication orpatent was specifically and individually indicated to be incorporated byreference.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

1-76. (canceled)
 77. A method for diagnosing a condition in a patient inneed thereof, comprising administering to the patient a pharmaceuticalcomposition comprising (a) a plurality of particles, each particlecomprising: (i) a pharmaceutically acceptable polymer core, selectedfrom the group consisting of poly(lactic-co-glycolic) acid (PLGA),poly(D,L-lactic-co-glycolic) acid), polyethylenimine,dioleyltrimethyammoniumpropane/dioleyl-sn-glycerolphosphoethanolamine,and polysebacic anhydride; and (ii) a poly(ethylene glycol) (PEG) havinga molecular weight of about 300 Da, about 600 Da, or about 1 kDadisposed on the outer surface of the polymer core by covalent linkage ata density of greater than 0.01 units/nm², wherein the particle has aparticle size between 150 nm and 750 nm in diameter; (b) an imagingagent, wherein the imaging agent is (i) disposed on or coated on thesurface of the pharmaceutically acceptable polymer core or the PEG; or(ii) covalently attached to the pharmaceutically acceptable polymer coreor the PEG; and (c) one or more pharmaceutically acceptable excipientsor carriers; wherein the pharmaceutical composition crosses a mucosalbarrier.
 78. The method of claim 77, wherein the PEG is disposed on thepharmaceutically acceptable polymer core at a density of 1 unit/nm². 79.The method of claim 77, wherein the imaging agent is disposed on orcoated on the surface of the pharmaceutically acceptable polymer core orthe PEG.
 80. The method of claim 77, wherein the imaging agent iscovalently attached to the pharmaceutically acceptable polymer core orthe PEG.
 81. The method of claim 77, wherein the pharmaceuticallyacceptable polymer is a biodegradable pharmaceutically acceptablepolymer
 82. The method of claim 77, wherein the particle has a zetapotential of between −10 mV and 10 mV, between −10 mV and 5 mV, between−5 mV and 5 mV, or between −2 mV and 2 mV.
 83. The method of claim 77,whereby the particle moves in human cervicovaginal mucus at adiffusivity of more than 4×10⁻² μm²/s at a time scale of 1 s.
 84. Themethod of claim 77, wherein the imaging agent is hydrophobic, compriseshydrogen bond donors or acceptors, or is charged.
 85. The method ofclaim 77, wherein the PEG has a molecular weight of about 1 kDa.
 86. Themethod of claim 77, wherein the biodegradable pharmaceuticallyacceptable polymer hydrophobic, comprises one or more hydrogen bonddonors or acceptors, or is charged.
 87. The method of claim 77, whereinthe biodegradable pharmaceutically acceptable polymer is apoly(D,L-lactic-co-glycolic) acid.
 88. The method of claim 77, whereinthe mass of the PEG makes up at least 1/3400, 1/2000, 1/1000, 1/500,1/200, 1/100, 1/50, 1/20, 1/5, 1/2, or 9/10 of the mass of the particle.89. The method of claim 77, wherein the radioactive agent is aradioactive heavy metal, a radioactive chelate, ⁴³K, ⁵²Fe, ⁵⁷Co, ⁶⁷Cu,⁶⁷Ga, ⁶⁸Ga, ¹²³I, ¹²⁵I, ¹³¹I, ¹³²I, or ⁹⁹Tc.
 90. A method of deliveringa radioactive agent to a tissue, comprising administering to a patient apharmaceutical composition comprising (a) a plurality of particles, eachparticle comprising: (i) a pharmaceutically acceptable polymer core,selected from the group consisting of poly(lactic-co-glycolic) acid(PLGA), poly(D,L-lactic-co-glycolic) acid), polyethylenimine,dioleyltrimethyammoniumpropane/dioleyl-sn-glycerolphosphoethanolamine,and polysebacic anhydride; and (ii) a poly(ethylene glycol) (PEG) havinga molecular weight of about 300 Da, about 600 Da, or about 1 kDadisposed on the outer surface of the polymer core by covalent linkage ata density of greater than 0.01 units/nm², wherein the particle has aparticle size between 150 nm and 750 nm in diameter; (b) a radioactiveagent (i) disposed on or coated on the surface of the pharmaceuticallyacceptable polymer core or the PEG; or (ii) covalently attached to thepharmaceutically acceptable polymer core or the PEG; and (c) one or morepharmaceutically acceptable excipients or carriers; wherein thepharmaceutical composition crosses a mucosal barrier to delivery theradioactive agent to the tissue.
 91. The method of claim 90, wherein thepharmaceutically acceptable polymer is a biodegradable pharmaceuticallyacceptable polymer
 92. The method of claim 90, whereby the particlemoves in human cervicovaginal mucus at a diffusivity of more than 4×10⁻²m²/s at a time scale of 1 s.
 93. The method of claim 90, wherein the PEGhas a molecular weight of about 1 kDa.
 94. The method of claim 90,wherein the biodegradable pharmaceutically acceptable polymer is apoly(D,L-lactic-co-glycolic) acid.
 95. The method of claim 90, whereinthe mass of the PEG makes up at least 1/3400, 1/2000, 1/1000, 1/500,1/200, 1/100, 1/50, 1/20, 1/5, 1/2, or 9/10 of the mass of the particle.96. The method of claim 90, wherein the radioactive agent is aradioactive heavy metal, a radioactive chelate, ⁴³K, ⁵²Fe, ⁵⁷Co, ⁶⁷Cu,⁶⁷Ga, ⁶⁸Ga, ¹²³I, ¹²⁵I, ¹³¹I, ¹³²I, or ⁹⁹Tc.